D2C marketing agency case studies show what’s actually possible when brands partner with the right agencies. But reading case studies requires knowing what to look for and what to question.
According to research from UpCounting analysing ecommerce ROAS benchmarks, average ecommerce ROAS dropped to 2.87 in 2025 as advertising costs rose, which means many older case studies showing dramatically higher returns may no longer reflect current reality.
This guide helps you understand what realistic agency results look like, how to evaluate case studies critically, and what outcomes you should expect when working with a D2C marketing partner.
What Good Agency Results Actually Look Like
Before examining case studies, understand what constitutes genuinely good performance in today’s environment.
Realistic ROAS expectations. Average ecommerce ROAS varies significantly by category. Fashion brands typically see 3.0 to 4.0x returns on paid social. Beauty and skincare often perform between 2.5 and 3.5x due to longer consideration cycles. Supplements can achieve higher returns because subscription models boost lifetime value. When agencies claim 8x or 10x ROAS, ask detailed questions about how that was measured and whether it includes branded traffic.
Meaningful efficiency improvements. Strong agencies typically improve ROAS by 20-40% within the first six months through better targeting, creative optimisation, and campaign structure. Claims of doubling or tripling ROAS overnight should trigger scepticism unless there were obvious problems being fixed.
Sustainable scale increases. Good agencies help brands increase spend while maintaining or only slightly decreasing efficiency. Scaling ad spend by 30-50% while keeping ROAS within 15% of previous levels represents genuine skill. Agencies that scale spend dramatically while ROAS collapses aren’t demonstrating expertise.
Revenue growth that matters. The ultimate measure is profitable revenue growth. Case studies showing revenue increases mean nothing without context about margins, ad spend, and whether the growth was actually profitable.
How to Read Agency Case Studies Critically
Most agency case studies present results in the best possible light. Here’s how to evaluate them properly.
Question the baseline. When a case study claims “increased ROAS by 200%,” ask what the starting point was. Improving ROAS from 1.0x to 3.0x means something different than improving from 3.0x to 9.0x. Many dramatic improvements come from fixing obviously broken campaigns rather than demonstrating sophisticated optimisation.
Understand the time frame. Short-term results often don’t hold. A case study showing amazing results from a three-month period may not reflect sustainable performance. Look for case studies covering six months or longer to understand whether improvements lasted.
Separate branded from non-branded. Many impressive ROAS numbers include branded search and retargeting traffic that would likely have converted anyway. Ask whether results reflect true prospecting performance or blended numbers that obscure how hard the agency worked for new customer acquisition.
Consider external factors. Sometimes brands improve dramatically because of product launches, seasonal trends, or market conditions rather than agency expertise. Good case studies acknowledge these factors rather than claiming all credit for growth.
Check for cherry-picking. Agencies showcase their best results, not average performance. One exceptional case study doesn’t mean you’ll achieve similar outcomes. Ask about typical results across their client base, not just standout successes.
Common Patterns in Successful Agency Partnerships
Across genuine success stories, certain patterns emerge consistently.
Foundation fixing delivers quick wins. Many brands come to agencies with obvious problems: poor campaign structure, weak creative, broken tracking, or inefficient targeting. Fixing these fundamentals often produces dramatic short-term improvements. These wins are real but don’t necessarily reflect the agency’s ability to optimise already-good accounts.
Creative refresh drives performance. One of the most common sources of improvement is simply producing better creative at higher volume. Brands running the same ads for months often see immediate lifts when agencies introduce fresh concepts and systematic testing. Understanding how the Facebook algorithm works helps explain why creative refresh matters so much.
Proper measurement changes the picture. Sometimes agencies “improve” results primarily by implementing better attribution. When brands move from last-click to multi-touch attribution, or fix broken tracking, reported performance often looks dramatically better without actual campaign changes. This isn’t fake improvement, but it’s different from genuine optimisation.
Channel expansion unlocks growth. Brands heavily reliant on one channel often see significant gains when agencies add complementary platforms. A brand running only Meta ads might see substantial improvements when a D2C marketing agency adds Google Shopping or expands into new Meta placements effectively.
What Results Should You Expect?
Set realistic expectations based on your starting point.
If your current performance is poor. Brands with ROAS below 2.0x or with obvious campaign problems can often see 50-100% improvements in the first three to six months. There’s significant low-hanging fruit to capture when fundamentals are broken.
If your current performance is average. Brands already achieving category-average ROAS should expect more modest improvements of 15-30% as agencies optimise and test systematically. Dramatic improvements are less likely when basics are already sound.
If your current performance is strong. Brands already performing well should focus on scale rather than efficiency. Good agencies help you spend more while maintaining performance rather than promising to dramatically improve already-optimised accounts.
Timeline expectations. Expect the first one to two months to focus on auditing, restructuring, and establishing baselines. Months three and four typically show initial improvements as changes take effect. Months five and six should demonstrate whether improvements are sustainable and scalable.
Red Flags in Agency Case Studies
Watch for these warning signs when evaluating case studies.
Vague metrics without context. Case studies claiming “500% revenue growth” without explaining ad spend, margins, or time frames are hiding important details. Demand specific numbers with full context.
Short time frames only. Results from one-month or single-campaign periods often don’t reflect sustainable performance. Be sceptical of case studies that don’t show longer-term outcomes.
No discussion of challenges. Every client engagement involves setbacks and learning curves. Case studies presenting only smooth sailing probably aren’t telling the full story.
Unrealistic claims for your category. If an agency’s case studies all show 8x+ ROAS but industry benchmarks sit around 3x, either they only take clients in specific situations or they’re measuring differently than standard practice.
Inability to provide references. Good agencies connect you with clients who can discuss their experience directly. Reluctance to provide references suggests case study results may not hold up to scrutiny.
Questions to Ask About Specific Case Studies
When reviewing agency case studies, ask these questions.
What was the starting point before you began working together? Understanding the baseline helps you assess whether improvements reflect genuine skill or simple fixes.
What was the total time frame, and did results hold beyond the initial period? Sustainable performance matters more than short-term wins.
How do you separate branded and non-branded performance in these results? This reveals whether impressive ROAS reflects true new customer acquisition.
What challenges did you face, and how did you address them? Honest agencies discuss obstacles rather than presenting perfect narratives.
Can I speak with this client directly? Reference conversations reveal whether case study claims match client experience.
What was different about this client that made these results possible? Understanding what made results achievable helps you assess whether similar outcomes are realistic for your situation.
Using Case Studies in Your Decision Process
Case studies should inform your agency selection but not determine it entirely.
Look for relevant experience. Prioritise case studies from brands similar to yours in category, scale, and growth stage. A case study from a £50M brand may not be relevant if you’re doing £500K annually.
Evaluate the approach, not just outcomes. How agencies describe their process often reveals more than headline results. Look for systematic thinking, clear methodology, and honest assessment of what worked.
Combine case studies with references. Case studies show what agencies want you to see. Reference calls reveal what clients actually experienced. Use both to form a complete picture.
Trust patterns over outliers. One exceptional case study means less than consistent solid results across multiple clients. Ask about typical outcomes, not just best-case scenarios.
Making Your Decision
The best D2C marketing agencies present case studies honestly, acknowledge context and limitations, and connect you with clients who can verify their experience. Be sceptical of agencies whose case studies all show dramatic improvements without explaining how or why, and prioritise partners who discuss realistic expectations based on your specific situation.
Strong agency partnerships produce genuine value, but that value looks different depending on your starting point. Focus on finding partners who understand your situation and can articulate realistic outcomes rather than chasing agencies with the most impressive-looking case studies.
