Google’s Performance Max (PMax) is one of the most powerful automated advertising tools ever built—but out of the box, it comes with a major structural flaw that trips up founders and growth leads every single day: Brand Cannibalization.
When left unconstrained, PMax algorithms will naturally hunt for the easiest possible conversions to hit their Target ROAS. And what is the easiest conversion on the internet?
Someone typing your exact brand name into Google Search.
The Illusion of a 10x ROAS
Consider this scenario:
- Your PMax campaign reports a stellar 8.5x ROAS.
- You celebrate and increase the daily budget by 50%.
- Yet, total company revenue barely moves, and your customer acquisition cost (CAC) on new buyers actually worsens.
Why? Because PMax was bidding $1.80 per click on people who were already searching for your brand name, taking credit for transactions that would have happened organically or through a standard brand search ad costing $0.15 per click.
Meanwhile, non-brand prospecting (Shopping, YouTube, Display, Discover) was completely starved of budget.
How to Fix It: The 3-Step Remediation Plan
Step 1: Create a Brand Exclusion List
Inside Google Ads:
- Navigate to Tools & Settings → Shared Library → Brand Lists.
- Click + New Brand List and search for your brand. If your brand is not in Google’s directory, submit a verification request.
- Apply this Brand List as an Exclusion in your PMax campaign settings.
Now, PMax is strictly prevented from bidding on any search term containing your brand name or misspellings.
Step 2: Build an Isolated Brand Search Campaign
Never let brand defense disappear entirely, or competitors will bid on your name.
- Set up a standard Search campaign targeting
[your brand name]with Exact Match. - Use a Target Impression Share bidding strategy set to 95%+ at the absolute top of the page.
- Add negative keywords for support, logins, careers, or refund terms to prevent wasted spend.
Step 3: Segment PMax Feeds by Margin
Once PMax is restricted to non-brand prospecting, feed optimization becomes critical. Use Custom Labels in Google Merchant Center to split your product catalog:
- Heroes: High margin, high volume products (lower Target ROAS).
- Zombies: Products that haven’t received impressions in 30 days (isolate into a catch-all test campaign).
- Clearance: Low margin clearance items (high Target ROAS to prevent unprofitable ad delivery).
Conclusion
Performance Max is extraordinary at finding new customers across the entire Google ecosystem—when forced to do so. By placing brand guardrails on PMax, you separate real incremental growth from automated credit-stealing.