How to choose an ecommerce marketing agency depends on the decision you need help with. If you need a channel run well, judge execution and access. If you need to know where the next euro should go, judge how the agency checks results against your sales and margin. In both cases: you own the accounts, you know what they earn, and they can tell you what they don't know yet.
Many guides to choosing an agency are written by agencies. This one is too. So we will try to make it useful even if you never call us, and we will say when we are the wrong choice.
Start with the decision, not the agency. Write down the one question you want answered in the next six months. Then pick the kind of agency that answers it.
"Run this channel properly."
You need hands on the account, creative and a clear weekly view. A channel specialist can be enough.
"Should we spend more, and where?"
You need someone who ties spend to your contribution margin: what is left per order after product, delivery, payment, returns and discounts. The platform's ROAS alone will not answer this.
"We have no team for this."
Then the comparison is wider than agency against agency. See agency vs in-house paid media for that trade-off.
A performance agency and a full-service agency are not better or worse. They answer different questions. Hiring the wrong type is the expensive mistake, not hiring the wrong logo.
The table is a checklist, not a ranking. Ask the questions and listen for the answers that dodge.
You know your margin, you trust your measurement, and one channel needs better execution. Judge them on access, creative output and how fast they tell you something is not working. Our channel pages show what that scope looks like for Paid media (Meta, Google, TikTok) for ecommerce.
Marketing says "it works" and finance asks "so what?". You need someone who asks what would have happened without the spend. That is incrementality. The answer may come from a test, from a model or from reading the trend in your own sales. See how we scope Measurement & incrementality.
The problem sits outside the ad account. Stock, delivery, promotions, returns and cash all decide whether growth pays. An agency that only sees the panel will optimise the panel.
1. Account ownership. One agency's own list of red flags includes clients not having access to their ad accounts1. If the agency owns the accounts, leaving means starting from zero. Get ownership in writing. For the exit side, read how to switch marketing agency.
2. Conflicts of interest. Ask: "Do you earn anything from the tools you recommend to us?" Referral fees and partnerships are common and not always bad. Not telling you is. An agency selling fixed retainers argues that pricing as a percentage of ad spend creates a conflict of interest2. It sells the alternative, so read that as a view. The fee options are compared in percentage of ad spend vs flat fee vs revenue share, and one of them is unpacked in revenue share agency contract.
3. Who wrote the comparison. Measurement vendors publish comparisons of measurement vendors. One such comparison is written by a vendor that is also one of the products compared3. Nothing wrong with that, as long as you know who is marking the homework. The same applies to recommendations: in a 2010 Hacker News thread asking for PPC agency suggestions, some replies came from people selling PPC services or tools4.
4. Honesty about limits. A tool vendor's list of what clients dislike about agencies includes promises that were not kept5. An agency that is certain about everything in month one is guessing confidently. Ask what they can't measure yet.
5. Reports you can read. A report should tie spend to orders, sales and margin. If it leads with reach and clicks, ask what changed in the bank account. See how to read an agency report.
For the longer lists, we keep separate pages on marketing agency red flags and questions to ask a paid media agency.
Choose by the decision you need to make, then by honesty. Execution is easier to judge than people think: ask for access and look. Honesty is harder to judge, and it costs more when it is missing.
Ask every agency the same question: "What would make you say we're not a good fit?" An agency that can't answer will take any client, including the ones it can't help. One agency's guide to choosing a Google Ads agency has a section on who it is not a fit for6. We think every agency should have one.
For ZFD: We follow the money, all the way to the bank. If a channel looks great in the panel and leaves nothing after costs, we say so before we ask for more budget.
It depends on where the problem sits. If one channel needs better execution, a specialist can be enough. If the question is whether growth pays after costs, you need someone who looks beyond the ad account.
You should, in writing. The agency works inside your accounts. That way leaving does not mean starting again.
Not by itself. Referral fees and partnerships are common. Not disclosing them before you sign is the problem.
Ask how results were checked against orders, sales and margin, and which method was used. Platform ROAS on its own is the platform's view, not proof.
“Their engagement is impressive.”
Start with a free audit of your measurement, ad accounts, CRO or retention. Or book a call about your budget decision. If someone else is the better fit, we will say so.
