Glassdoor As Agency Due Diligence: The Step Nobody Takes Before Signing

Most agency due diligence checklists are predictable. Review the case studies. Talk to two references. Verify team tenure. Confirm pricing. Sign the SOW.

There is one source of intelligence about an agency that almost nobody checks before signing, and it tells you more about what your engagement will actually look like than any case study or reference call. That source is Glassdoor.

Here is why agency Glassdoor reviews matter more than case studies, what to actually look for, and how to use them to predict whether your engagement delivers or quietly collapses in month four.

The one source of agency intelligence almost nobody checks—and it tells you more about your future engagement than any pitch deck ever could.

Why This Step Gets Skipped

Agency selection in 2026 still leans heavily on the sales process. You watch the pitch, evaluate the deck, talk to the senior team, and make a call. The senior team you meet during the sales process is rarely the team that manages your account. That is not malice. That is how agencies are structured.

What predicts whether your account team will be good, available, and still employed in six months is not pitch quality. It is the operational health of the agency as a workplace. Burned-out account managers, high turnover, and resentful junior staff are invisible during a sales process and very visible by month three of an engagement.

Glassdoor surfaces that. It does so anonymously, without the agency curating the narrative.

The reason this step gets skipped is not that it does not matter. Most procurement and marketing leaders simply have not been taught to look there. Agency due diligence frameworks were built before Glassdoor existed.

What Agency Turnover Actually Costs You

If you hire an agency with 50% annual turnover, here is what your year looks like in practice.

• Month 1: The senior strategist who pitched you is on the account. Things are strong.
• Month 2 to 3: That senior strategist “transitions to other clients.” A junior account manager is your new day-to-day contact.
• Month 4: The junior account manager gives notice. They are technically still on the account for two weeks.
• Month 5: A new junior account manager is onboarded. They start asking your team for context you already provided to the previous two contacts. Your work stalls.
• Month 6 to 7: Productive work resumes. The new account manager is competent.
• Month 8 to 9: They give notice or move to a different account.

That is roughly four to five months of productive work out of twelve, even when the agency is technically capable. The rest of the engagement is spent re-onboarding people who do not have your context.

This pattern is well-documented and almost never disclosed during the sales process.

The RBM Number, in Context

We sit at 4.2 out of 5 on Glassdoor with 74% of employees recommending Red Branch Media to a friend. I’m citing this here not as a brag but because it belongs in any honest agency due diligence conversation, and it is the easiest number for me to be transparent about.

For context, the median B2B marketing agency on Glassdoor sits closer to 3.4 to 3.7 with recommendation rates between 50% and 65%. Agencies that cluster below 3.5 stars tend to share common traits: high turnover, utilization expectations above sustainable rates, junior-heavy account staffing, and senior people who burn out and leave inside 18 months.

Agencies that cluster above 4.0 and above 70% recommendation tend to share different traits: senior people stay for years, account team composition is stable, and the people who pitched you are usually still around when the engagement is up for renewal.

Check the number for any agency you are evaluating. Not because it tells the entire story, but because it is a leading indicator for every problem that will surface in your engagement six months from now.

What to Actually Look For on Agency Glassdoor

Past the star rating, here is the diagnostic.

Tenure of the reviewers. If most negative reviews are from people who lasted 6 to 12 months, the agency has a retention problem. If most reviews are from people who lasted 18 months or more, the agency is at least keeping people long enough to develop real productivity.

Specific mentions of client work. Reviews that say “stretched across too many clients” or “no time to do good work” tell you the agency is over-utilizing its team. That over-utilization will show up in your account too.

Senior leader patterns. Multiple negative reviews mentioning the same senior leader by name or unmistakable role is a real signal. Most agencies have one founder or partner who drives culture. If reviews suggest that person is the source of dysfunction, the agency will not improve quickly.

The “pros” section. If the most positive reviewers can only name “free snacks” and “remote work,” the work itself is probably not satisfying. People who work at good agencies talk about the clients, the colleagues, and the craft. People who work at struggling agencies talk about the perks.

The pattern of complaints. Two negative reviews could be outliers. Twenty negative reviews with the same complaint about turnover, workload, or leadership represent a pattern. Patterns predict your experience.

How This Maps to Client Engagement Quality

Glassdoor does not tell you whether an agency is creative or strategic. It tells you whether the agency has the operational health to deliver consistently over a 12- to 24-month engagement.

A creative, strategic agency with operational health delivers strong work for the duration of your contract.

A creative, strategic agency with operational dysfunction delivers one strong quarter, then declining quality as people burn out and rotate off your account.

When the pitch and the Glassdoor profile contradict each other, the Glassdoor profile is closer to what you will actually experience.

What to Ask in the Sales Conversation

If the Glassdoor profile raises concerns, ask three direct questions before you sign.

“What is your team’s average tenure on client accounts?”

A real answer includes numbers with context. A fluffy answer is a dodge.

“Who specifically will be on my account, and how long have they been at the agency?”

The agency that staffs your account with people who joined three months ago is not the agency you want. The one that staffs you with senior people who have been there for years is showing you they have the bench.

“What is your client retention rate, and how do you measure success?”

Strong agencies retain clients for years. The retention number is one of the cleanest signals in agency selection, and almost nobody asks for it.

If the agency cannot answer these questions cleanly, the engagement will be worse than the pitch suggested. Every time.

Before signing with any agency, ask for their team tenure, account staffing, and client retention rate. The answers—or the dodges—tell you everything.

When to Take Glassdoor Reviews with Some Caution

Glassdoor is a useful signal, buuuuut not a perfect one.

Sample size matters. An agency with 8 reviews and a 4.5 average is statistically noisier than one with 80 reviews and a 4.1 average. Bigger samples are more reliable.

Industry context matters. Marketing agencies as a category run lower on Glassdoor than tech companies broadly. A 3.8 at an agency may be roughly equivalent to a 4.2 at a software company. Compare agencies to each other, not to the broader Glassdoor baseline.

Recent reviews matter more than old ones. An agency that struggled three years ago and has rebuilt should be evaluated on recent reviews. Patterns from 2021 do not reflect 2026 reality.

One bad review is not the story. Look for patterns. Disgruntled outliers exist at every company. Patterns indicate culture.

With those caveats in mind, Glassdoor remains the single most underused source of agency intelligence in B2B marketing today.

The Bottom Line

Most agency due diligence frameworks were built when Glassdoor did not exist. They tell you whether the agency can do the work. They do not tell you whether the agency can do the work consistently over a 12- to 24-month engagement.

Glassdoor tells you the second part. It tells you whether the team that pitched you will still be there in month nine. It tells you whether the people doing the work are over-utilized to the point of burnout. It tells you whether the agency you are hiring is actually the one you will experience.

We advise clients to add Glassdoor review as a required step in any agency evaluation. It takes 20 minutes and saves an average of one bad agency engagement per year for any company that takes it seriously.

That is a higher ROI than most marketing investments. And it costs nothing.

Check the number before you sign.