How to choose an eCommerce agency as a fashion brand

A fashion brand looking for an eCommerce agency quickly receives several proposals that look alike. Same promises, same logos, same "dedicated team." The real difference lies elsewhere: knowledge of the sector, the people who actually run the account, and how the results are read.

Here are the criteria to check, the questions to ask before signing, and the warning signs to watch for.

Which criteria matter when choosing an eCommerce agency for a fashion brand?

Seven criteria make the difference: fashion specialization, team profile, number of partners, Shopify and Klaviyo expertise, reporting, the contract and the first audit. The table below sums up what to check for each one.

Why does an agency specialized in fashion make the difference?

Because fashion has constraints that a generalist agency discovers at your expense. Collections that rotate. Stock by size. High return rates. Sales periods and key moments that concentrate revenue. A campaign pushing a piece that's out of stock in most sizes wastes its budget. A product page without a size guide generates returns.

So ask for case studies from the sector, not just logos. A useful case study gives the starting problem, the actions taken, a quantified result and its time period. OMOSA works with fashion and lifestyle brands: ready-to-wear, knitwear, jewelry, lingerie. OMOSA has supported 50 brands since 2024.

Should you have one partner or one agency per lever?

A single partner for paid media, the site and CRM keeps the coordination from falling on you. With three agencies, each one moves forward on its own scope. The paid agency watches its ROAS, the CRM agency its open rate, the site agency its conversion rate. Nobody holds the overall vision, and decisions end up contradicting each other.

Several specialized agencies can work very well, on one condition: someone manages them. That's the role of an eCommerce lead. Either you have one in-house, or you hand it to a partner who takes it on for you.

That's what we did at Tressé, a ready-to-wear brand, from 2024 to 2026. OMOSA took on the eCommerce lead role and managed the paid and CRM agencies already in place. The site, returns and international were handled directly. The result: +62% eCommerce revenue in 2025 compared with 2024 (OMOSA x Tressé annual review, January 2026).

• +62%eCommerce revenue2025 vs 2024 · Annual review OMOSA x Tressé, January 2026
• +71%International revenue2025 vs 2024 · Annual review OMOSA x Tressé, January 2026
• +61%Revenue from existing customers2025 vs 2024 · Annual review OMOSA x Tressé, January 2026

How can you check who will actually work on your account?

Before signing, ask to meet the people who will run your account day to day. At many agencies, a senior profile leads the sale, then a junior profile takes over the account. You lose the context just as the work begins.

Also look at where these people come from. A consultant with brand-side experience has already managed stock, a P&L and trade-offs between channels. They know what an action plan demands of an in-house team. At OMOSA, the team counts 8 senior experts, with an average of 7 years of experience, who have worked at brands such as Jérôme Dreyfuss, L:A Bruket, Printemps and Faguo. No interns or work-study students.

Why does Shopify and Klaviyo expertise matter for a fashion brand?

Because most growing fashion brands sell on Shopify and send their emails and SMS through Klaviyo. An agency that knows both tools moves faster. It knows what an app adds to, or breaks on, the site. It knows how to segment a customer base and which flows to launch first: welcome, abandoned cart, post-purchase.

OMOSA is an official partner of Shopify, Meta and Google, and a Klaviyo Partner. Almost all the brands we support are on Shopify and Klaviyo.

How does a good agency report on its results?

A good agency reads its results on your margin, not on the number a platform displays. Meta's or Google's ROAS counts the sales the platform attributes to itself. It ignores product cost, discounts, shipping and returns. Two campaigns with the same ROAS can therefore have opposite profitability.

Ask to see a sample report. It should show the metrics that matter for your business: customer acquisition cost, advertising as a share of sales (COS), conversion rate, average order value, repeat purchase rate, customer lifetime value. And it should say what isn't working, not just what is.

At OMOSA, these metrics form a single scorecard shared across all three levers. You get a check-in every two weeks and a report every month.

What contract and first audit should you expect from an eCommerce agency?

Aim for a short, renewable commitment with a fixed, clear price. A firm one-year contract from day one is a lot for a relationship you haven't tested yet. Three months is enough to set a strategy, execute it and measure the first results.

The first audit says a lot about what comes next. A good audit starts from your numbers: P&L, conversion funnel, performance by channel, customer base. It ends with prioritized actions that you keep even if you don't sign.

At OMOSA, the commitment is three months, renewable quarterly, with 30 days' notice and a fixed monthly fee, with no variable component. The first conversation is free: 30 minutes with Axel, a few days analyzing your platforms, then a debrief with five actions for the following 30 days. The paid in-depth audit goes further and ends with a prioritized roadmap.

What questions should you ask an eCommerce agency before signing?

These eight questions are enough to tell most agencies apart. Ask them to every agency you meet. A vague answer is already an answer.

1. Which fashion brands do you work with, with what results, over what period?
2. Who will work on our account every week, and can we meet them before signing?
3. Have these people worked on the brand side?
4. Who coordinates paid media, the site and CRM?
5. Which metrics do you track, and how often do you report to us?
6. What happens if the results don't come?
7. How long is the commitment, and what is the notice period?
8. What does the first audit include, and what do we keep at the end?

What warning signs should you watch for in an eCommerce agency?

Certain signs come up again and again among brands disappointed by their agency. One on its own isn't enough to rule an agency out. Several together are.

• Case studies without figures, or figures without a time period.
• A senior contact during the sale whom you never see again afterwards.
• Reporting that only talks about platform ROAS.
• Reports where everything is always going well.
• Good results driven mostly by retargeting your existing customers, with no new customers.
• A long commitment before any audit.
• An agency that wants to take over everything, even what's working with your current providers.

When is OMOSA the right choice for a fashion brand?

OMOSA is a Paris-based eCommerce agency, founded in 2024 by Axel Corton, for fashion and lifestyle brands. A team of 8 senior experts from the brand side covers three levers: paid media (Attract), the site and eCommerce leadership (Activate), and CRM with Klaviyo (Retain). Our goal: take a brand from €1M to €5M in eCommerce revenue while staying profitable.

We're a good fit if your brand has already found its audience and wants to accelerate, with a single direction across its levers. You can also hand us just one lever: we work alongside your existing agencies, and we'll tell you frankly which ones are performing.

If your needs come down to one or two days a month, an agency probably isn't the right answer. We explain why in our article agency, freelancer or in-house hire.