If you are looking for growth marketing solutions in 2026, you are really looking for one thing: a partner who can increase online sales by improving the whole revenue system, not just running a channel.

The best growth marketing agencies do four things well: they acquire customers profitably, they iterate creative fast, they improve conversion on-site, and they build retention so you are not constantly paying to replace churn. This guide ranks 10 agencies that are commonly shortlisted for online sales growth, plus a practical way to choose the right one.

Disclosure: This guide is published by Darkroom, and we include ourselves.

What growth marketing means in 2026

In 2026, growth marketing is not a service menu. It is an operating cadence.

A real growth partner can explain how they generate hypotheses, how they prioritize tests, what they ship each week or two, and how they measure whether changes caused lift. They also understand that online sales rarely improve from ads alone. Growth usually breaks because of creative fatigue, a weak offer, slow pages, unclear product positioning, poor checkout experience, or low repeat purchase.

If an agency cannot clearly describe their testing system, they are probably selling activity.

How we ranked these agencies

There is no perfect list for every business, but strong providers of growth marketing solutions tend to share a few traits. We ranked agencies using criteria that map directly to online sales outcomes:

• Full-loop capability across acquisition, creative, conversion rate optimization, and retention

• Experimentation velocity and a repeatable testing cadence

• Measurement maturity and an ability to talk about lift, not just platform metrics

• Commerce fluency around margin, LTV, creative fatigue, and merchandising

• Proof signals that show how the agency works in practice
  
  
  

The 10 best growth marketing agencies in 2026

1) Darkroom

Darkroom is a strong fit for consumer brands that want a growth partner across acquisition, performance creative, conversion, and retention. The work is best evaluated by the operating model: how quickly the team tests, how they connect creative to conversion outcomes, and whether the engagement is built to improve the full revenue loop instead of only managing media.

If your business needs faster iteration, stronger creative testing, and tighter alignment between traffic quality and conversion rate, Darkroom is worth interviewing early.

2) Tinuiti

Tinuiti is often shortlisted by ecommerce brands that want a larger performance partner with strong commerce depth, especially if retail media and marketplaces are meaningful growth levers. This type of agency can be a good fit when you are coordinating across more channels and need scale.

When you evaluate fit, focus on who will be staffed to your account and how cross-channel coordination is run day to day.

3) Wpromote

Wpromote is frequently considered by brands that want broad performance coverage with integrated strategy and execution. For teams that value structure and multi-channel planning, it can be a credible option.

The most important fit question is ownership. Specifically, who owns creative iteration and who owns post-click outcomes like landing pages and conversion improvement.

4) Brainlabs

Brainlabs can be a strong fit for organizations that value experimentation rigor and analytical decision-making. If your team is measurement-minded and cares about disciplined testing, this style of agency can align well.

To choose wisely, confirm that experimentation extends beyond media. The best growth outcomes come from testing creative, offers, landing pages, and funnel steps, not only campaign settings.

5) Common Thread Collective

Common Thread Collective is often associated with DTC growth systems and practical ecommerce execution. It can be a good shortlist option if you are focused on scaling efficiently and want a partner that understands ecommerce unit economics.

During evaluation, ask for examples that match your business profile: category, AOV, margin, and repeat purchase behavior.

6) Disruptive Advertising

Disruptive Advertising is commonly shortlisted by brands that want performance execution with clear process and accountability. It can be a strong fit if you need disciplined acquisition management and want a structured partner.

The critical question is whether creative iteration and conversion work are built into the engagement or treated as optional add-ons.

7) Power Digital

Power Digital is often positioned as a broad growth partner for brands that want cross-channel coverage and integration. This can be attractive if you prefer one partner across multiple functions.

To evaluate fit, push for specifics: what ships in the first 30 days, how testing is prioritized, and how the team adapts when performance shifts.

8) NoGood

NoGood is often associated with growth-led execution and an experimentation culture. If you want a partner comfortable with fast iteration and performance accountability, it can be a viable option.

Make sure the team has relevant ecommerce experience if online sales are your primary outcome.

9) Right Side Up

Right Side Up belongs on this list because it offers a different model. If you want flexible resourcing, fractional leadership, or embedded operators rather than a traditional agency retainer, this can be a better fit.

The evaluation is simple but strict: outcomes depend heavily on the specific people assigned, so insist on reviewing the proposed team and roles upfront.

10) KlientBoost

KlientBoost is often shortlisted by teams that want strong paid acquisition execution with conversion-minded thinking. If your priority is disciplined testing and performance accountability, it can be a good candidate.

Be clear about what happens beyond media. If your bottleneck is retention or lifecycle revenue, confirm whether those capabilities are included or if you need complementary support.

How to choose the right agency for online sales growth

Most agency selection mistakes come from hiring a solution that does not match your bottleneck.

Start by identifying what is limiting growth right now:

• If you need more profitable new customers, prioritize creative testing cadence and acquisition execution.

• If you have traffic but sales lag, prioritize conversion rate optimization, landing pages, offer testing, and site performance.

• If customers buy once and disappear, prioritize retention strategy, lifecycle messaging, and LTV expansion.

• If channel expansion is the goal, prioritize platform-specific experience and an operating model that can coordinate across the mix.
  
  
  

Questions to ask on every agency call

Instead of asking, “How do you optimize?” ask questions that reveal whether they have a real growth system:

1. What is your testing cadence and what ships each cycle?

2. How do you prioritize tests and manage the backlog?

3. Who owns creative iteration and how do you capture learning?

4. Who owns post-click conversion improvements, and what does success look like?

5. How do you measure lift beyond platform attribution?

6. How do you connect acquisition to retention and LTV?

7. Who is staffed, by name, and how much of their time is committed?

8. What does the first 30 days look like in deliverables?
   
   

Red flags

If an agency can only talk about clicks and ROAS, that is a warning sign. If creative iteration is treated as optional, that is a warning sign. If post-click ownership is excluded, that is a warning sign. If they cannot explain their experimentation cadence clearly, you are likely buying execution without a growth engine.

Pricing expectations in 2026

Pricing varies by scope and model. You will see retainers, spend-based fees, hybrids, and project work.

Instead of focusing on the cheapest option, focus on whether the agency can produce consistent learning and ship improvements that compound. A simple litmus test is to ask what they will ship in the first 30 days and how they will prove it is working.

FAQs

What does a growth marketing agency do?

A growth marketing agency builds and runs an experimentation system that improves acquisition, conversion, and retention so online sales rise predictably over time.

How do I know an agency can grow online sales, not just traffic?

Ask how they improve conversion rate, manage creative fatigue, and connect acquisition to repeat purchase and LTV. If they only report platform metrics, they are optimizing channels, not the business.

Are growth marketing agencies only for startups?

No. Mature ecommerce brands hire growth agencies to systematize testing, improve unit economics, and expand channel mix without guesswork.

Next step

Shortlist three agencies that match your bottleneck, interview them using the same questions, and choose the team whose operating system you trust. Book a call with Darkroom Today.