How to Evaluate a Marketing Agency's Portfolio: 10 Things to Check Before Signing

In a nutshell: The portfolio is the first evaluation tool when choosing a marketing agency. Yet 62% of B2B decision-makers admit having reviewed it superficially before signing a contract (HubSpot, 2025). In this guide you'll find 10 concrete criteria — with questions to ask, red flags, and positive signals — to distinguish a genuine portfolio from an inflated one. It includes two operational tables, three approaches for requesting references, and a comprehensive FAQ section.

Why the portfolio is (still) the top evaluation criterion

In the process of selecting a marketing agency, the portfolio remains the first element analyzed by potential clients. According to a 2025 Clutch survey, 78% of companies examine the portfolio before even requesting a quote. This figure is no coincidence: the portfolio represents the only tangible proof of what an agency can do, before the salespeople's words enter the picture.

But there's a problem. Most portfolios are built to impress, not to inform. Screenshots without context, famous brand logos without explaining the agency's role, vague results like "increased brand awareness." The result is that many companies sign contracts based on a visual illusion, only to discover — months later — that the agency didn't have the promised capabilities.

A well-constructed portfolio is a strategic document. It tells not only what was done, but why, how, and with what measurable results. If an agency cannot present its work this way, that's the first sign something is off.

The Content Marketing Institute found that agencies with detailed case studies and quantifiable results have a lead conversion rate 3.2 times higher than those that only show screenshots. This suggests that portfolio quality is not just an indicator for the client, but a genuine business tool for the agency itself.

In this guide, we analyze the 10 fundamental elements to check when evaluating an agency's portfolio. Each point includes concrete questions to ask, positive signals to look for, and red flags to watch out for.

The 10 elements to check in a portfolio

1. Industry variety

A portfolio with work exclusively in one industry can be a sign of specialization — or a lack of flexibility. The ideal is finding a balance: an agency that has worked in at least 4-5 different sectors demonstrates strategic adaptability without losing depth.

According to Forbes (2025), agencies with cross-sector experience produce strategies that are 27% more innovative, because they apply best practices from one sector to another. If the agency only works with restaurants or only with SaaS companies, ask yourself whether it can truly understand the specific dynamics of your market.

Question to ask: "Which industries have you worked in over the past 24 months? Can you show me a case study in an industry similar to mine?"

Red flag: all the work is in the same sector and the agency doesn't explain why. Or, the listed sectors are generic ("SMEs," "e-commerce") with no specific details.

2. Case studies with measurable results (not just pretty images)

Images capture attention, but numbers build trust. A portfolio that only shows website screenshots or social posts without any performance data is an incomplete portfolio. According to AgencyAnalytics (2025), 68% of agencies that include metrics in their case studies close contracts faster.

An effective case study should include: the client's initial objective, the strategy adopted, the concrete actions taken, and the numerical results (traffic, conversions, leads, revenue). Without these elements, you're looking at a photo album, not a professional portfolio.

Question to ask: "What metrics did you track for this project? Can I see the before/after data?"

Red flag: the agency responds with vague phrases like "we improved their online presence" or "the client was very satisfied" without supporting data.

3. Verifiable clients (are they real? can you contact them?)

A logo in a portfolio means nothing if you can't verify the relationship. According to a 2024 Clutch report, 23% of agencies include work in their portfolio for which their actual role was marginal — a single social post, a one-hour consultation, or a project never completed.

Verification is simple: search for the client on LinkedIn, check if the project is actually live, and ask the agency if you can speak directly with the contact person. A reputable agency will have no problem connecting you with their clients.

Question to ask: "Can I speak directly with the marketing director of this client?"

Red flag: the agency refuses or stalls, citing "confidentiality" reasons for every single client. Confidentiality is legitimate in some cases, but not for the entire portfolio.

4. Consistency between portfolio and services offered

If an agency positions itself as an SEO specialist but the portfolio only shows graphic design work, there's a consistency problem. This doesn't mean the agency can't do SEO, but it has no evidence to show — and that should give you pause.

HubSpot (2025) found that 41% of companies that chose an agency where services and portfolio didn't align terminated the relationship within the first 6 months. Consistency between what the agency claims to do and what it demonstrates having done is a fundamental indicator of reliability.

Question to ask: "Can you show me a specific case study for the service you're proposing to me?"

Red flag: the agency has a rich portfolio but all the work relates to services different from the one you need. Or, the portfolio is generic and not organized by service.

5. Freshness (recent work vs. work from 5 years ago)

Digital marketing changes radically every 18-24 months. A portfolio with work dated 2021 or 2022 is an obsolete portfolio. The strategies, platforms, and best practices from three years ago are largely outdated. An agency that doesn't update its portfolio is communicating — even unintentionally — that it has no recent work to show.

A healthy portfolio should contain at least 60% of work from the last 12 months and the remaining 40% from the last 24 months. Anything older should be in a separate "archive" section.

Question to ask: "When was this project completed? Do you have more recent work in this area?"

Red flag: the most recent work in the portfolio dates back more than 18 months. Or, dates aren't listed (which might be intentional).

6. Client size (SMEs or enterprise only?)

An agency that primarily works with multinational corporations might not be the ideal choice for an SME with a limited budget — and vice versa. The size of clients in the portfolio tells you a lot about the cost structure, internal processes, and level of attention you can expect.

According to Forrester (2024), SMEs that choose agencies accustomed to working with enterprise clients spend an average of 35% more than the market benchmark, without achieving proportionally better results. The reason: enterprise processes (extensive briefs, multiple approvals, complex reporting) don't suit the speed and flexibility an SME needs.

Question to ask: "What's the average size of your clients? How many SMEs do you currently have in your portfolio?"

Red flag: the portfolio shows only large brand logos, but the agency has no experience with SME-typical budgets and timelines.

7. Case study depth (strategy, execution, results)

A two-line case study is worse than no case study at all. The depth with which an agency describes its projects is directly proportional to the quality of work performed. A complete case study should follow the structure: context > challenge > strategy > execution > results > learnings.

Agencies ranked in the Clutch Top 1000 dedicate an average of 800-1,200 words per case study, with charts, screenshots, and project timelines. This level of detail demonstrates not just competence, but also the ability to document and systematize their work.

Question to ask: "Can you send me the complete case study for this project, including the initial strategy and final results?"

Red flag: the case study is a single sentence with a screenshot. Or, the agency has no written case studies and proposes only an oral presentation.

8. Linked references and testimonials

Generic testimonials ("Great job, we're very satisfied!") have zero informational value. A useful testimonial is specific, attributed to a real person with name, title, and company, and linked to a visible project in the portfolio.

92% of B2B buyers read reviews before making a purchasing decision (G2, 2025). But in the agency context, reviews on third-party platforms (Clutch, Google, Trustpilot) carry much more weight than self-selected testimonials on the agency's website.

Question to ask: "Do you have reviews on Clutch or Google? Can I read the testimonials from clients of the projects you've shown me?"

Red flag: all testimonials are anonymous or unlinked to a specific project. Or, the agency has no presence on any review platform.

9. Presence of metrics (traffic, leads, ROI — not just "brand awareness")

"Brand awareness" is important, but it's not reliably measurable without specific (and expensive) tools. When an agency reports "increased brand awareness" as its only result, in most cases it means nothing else was measured.

The metrics that matter depend on the objective: organic traffic (SEO), conversion rate (CRO), cost per lead (advertising), engagement rate (social media), overall ROI (integrated strategy). According to AgencyAnalytics, agencies that track and report at least 5 KPIs per project have a contract renewal rate of 73%, compared to 41% for those that don't.

Question to ask: "What KPIs did you agree on with the client at the start of this project? How did you track them?"

Red flag: the only metric mentioned is "brand awareness" or "visibility." No numerical data in the case study.

10. Transparency about what the agency did vs. the client

This is the most underrated point, yet also the most revealing. In many projects, success is the result of a collaboration between agency and client. A transparent agency clearly specifies its own contribution: "We managed the SEO strategy and content creation, while the client handled the commercial side and customer service."

An agency that claims 100% of the credit for results is likely exaggerating. No agency works in complete isolation. Forbes (2024) highlighted that transparency in role division is one of the top indicators of professional maturity in the industry.

Question to ask: "In this project, what exactly was your role? What did the client manage internally?"

Red flag: the agency presents every project as exclusively its own success, with no mention of the client's contribution or other partners.

Portfolio evaluation checklist

Genuine portfolio vs. inflated portfolio

Not all portfolios are created equal. Here are the 5 key differences between an authentic portfolio and one built to impress without substance.

How to ask for references without seeming intrusive

Requesting references is a potential client's right, yet many business owners feel uncomfortable doing so. Here are three approaches that work, tested by hundreds of B2B buyers according to a Gartner (2024) analysis.

Approach 1: the contextualized request

Instead of asking generically "Can I speak with one of your clients?", connect to a specific project in the portfolio: "I saw the project you did for [company X]. Would it be possible to have a brief conversation with their contact person? I'd like to understand how the collaboration developed over time."

This approach works because it shows you've studied the portfolio carefully and your interest is genuine. The agency will perceive the request as a sign of seriousness, not mistrust.

Approach 2: the relationship duration question

A key indicator of an agency's quality is the average duration of client relationships. Ask: "How long have you been working with the clients you showed me in the portfolio? What's the average length of your contracts?"

If the answer is "6-12 months," you have a data point. If it's "3-5 years," you have a very different data point. Agencies with long-lasting relationships won't have any problem sharing this information. According to HubSpot (2025), the average duration of a B2B agency-client relationship is 2.3 years — under 12 months is a warning sign.

Approach 3: the mini-audit request

Some agencies offer free or low-cost audits as a first step toward collaboration. If the portfolio convinces you but you want concrete proof before signing, ask: "Would you be willing to do a preliminary analysis of my current website/strategy? Even on a paid basis — it would help me understand your approach."

An agency that accepts is demonstrating confidence in its capabilities. An agency that categorically refuses might have something to hide — or simply a rigid sales process. Either way, the response tells you a lot about their company culture.

Frequently Asked Questions (FAQ)

How many projects should a good portfolio have?

There's no magic number, but a portfolio with fewer than 8-10 case studies is generally too thin to reliably evaluate an agency. The ideal is between 15 and 30 projects, organized by sector or service. More important than quantity is quality: 10 detailed case studies with measurable results are worth more than 50 contextless screenshots. Clutch recommends at least 10 verifiable projects as the minimum threshold for certified agencies.

Is it normal for an agency not to show all its clients?

Yes, it's perfectly normal. Many contracts include confidentiality clauses (NDAs) that prevent the agency from naming the client or publicly showing results. According to a Forbes (2024) survey, approximately 35% of agency projects are covered by NDAs. A reputable agency will explain which projects it can't show and why, perhaps offering anonymized versions of case studies. The red flag triggers when no client is verifiable.

How can I tell if the portfolio results are real?

Three concrete strategies: (1) ask for analytics tool screenshots with visible dates — a Google Analytics or SEMrush report is hard to fake; (2) verify data with public tools like SimilarWeb or Ahrefs for organic traffic; (3) contact the client directly to confirm results. Agencies that operate transparently will have no problem with any of these requests. If the agency refuses all three, seriously consider looking elsewhere.

Is the website portfolio enough, or should I ask for additional material?

The website portfolio is almost always a simplified version. Always ask for complete case studies in PDF format or in a dedicated presentation. Website portfolios tend to prioritize visual impact over informational depth. A well-structured agency will have additional material ready to share: slide decks, results reports, project timelines. If the website portfolio is all they have, it's a sign that internal documentation may be lacking.

How important is the portfolio's design itself?

The portfolio's design is a meta-indicator: if an agency can't present its own work well, how will it present yours? That said, don't confuse a visually appealing portfolio with a useful one. Some of the best portfolios we've analyzed were simple, well-structured PDF documents with no animations or special effects. What matters is that the information is organized, complete, and easily navigable. A beautiful but empty portfolio is worse than a simple but content-rich one.

How do I objectively compare the portfolios of two agencies?

Use the evaluation table in this guide as a comparison grid. Assign a score from 1 to 5 for each of the 10 criteria, then compare the totals. But be careful: don't choose solely based on score. An agency with an overall score of 35/50 but a 5/5 on the criterion most important to you might be preferable to one with 40/50 but a 2/5 on that specific criterion. Weight the criteria based on your actual priorities, not uniformly.

Can an agency without a portfolio still be valid?

In theory, yes — a newly founded agency with experienced professionals might not yet have a company portfolio. But in practice, the risk is high. If the agency is new, ask for the individual portfolios of the founders and key team members. If no one on the team has a verifiable track record, you're essentially betting on a promise. According to HubSpot, agency startups with founders who have a solid personal portfolio have a 64% success rate in their first 3 years, compared to 28% for those without any documented track record.

Sources and references

• Clutch — Global Agency Survey 2024-2025: data on client verifiability, case studies, and agency certifications. clutch.co/resources
• HubSpot — State of Marketing Report 2025: statistics on agency-client relationship duration, service-portfolio consistency, and B2B lead conversion. hubspot.com/state-of-marketing
• Forbes — Agency Transparency Index 2024: analysis of agency transparency, cross-sector experience, and NDA clauses in the industry. forbes.com/advisor
• AgencyAnalytics — Agency Benchmarks Report 2025: data on performance metrics, KPI tracking, and correlation with contract renewals. agencyanalytics.com/blog
• Forrester — B2B Agency Selection Survey 2024: benchmarks on SME vs. enterprise spending and the impact of agency size on performance.
• Content Marketing Institute — B2B Content Marketing Benchmarks 2025: data on the effectiveness of detailed case studies in lead generation.
• G2 — Buyer Behavior Report 2025: statistics on the weight of reviews in B2B purchasing decisions. g2.com/reports
• Gartner — CMO Spend Survey 2024: data on marketing budget allocation and trends in agency selection.