In a Google Ads account running multiple campaign types like Search, Performance Max (PMax), and Demand Gen, cross-campaign cannibalisation happens when these campaigns compete for the same users, search queries, or placements. This internal overlap leads to wasted ad spend, inflated CPCs, and difficulty in optimising performance.

For example, PMax might start capturing branded search traffic meant for your Search campaigns, or Demand Gen might overlap with Display or remarketing efforts, causing attribution confusion and budget inefficiency.

This blog post breaks down how cross-cannibalisation affects your overall ad strategy and provides actionable solutions to restructure your campaigns for better performance, cleaner data, and higher ROAS.

Cross-cannibalisation in a Google Ads account occurs when multiple campaigns (like Search, Performance Max, Demand Gen, etc.) compete for the same or similar audience/search queries, leading to inefficiencies in performance, inflated costs, and difficulty in attributing performance accurately.

Let’s break this down and then cover solutions.

How Cross-Cannibalisation Happens by Campaign Type

Common Symptoms of Cannibalisation

• Brand campaign impressions drop after launching PMax.
• CPCs or CPAs increase without clear attribution.
• Demand Gen campaigns deliver similar audience interactions as PMax.
• Search campaigns lose impression share even with high bids.
• Shopping campaigns underperform due to PMax taking over Shopping inventory.

Solutions to Avoid/Minimise Cross-Cannibalisation

1. Prioritise with Campaign Structure & Exclusions

2. Audience & Asset Differentiation

• Demand Gen vs PMax: Utilise custom segments and distinct creatives to target unique user journeys.
• Create audience exclusions across campaigns to control exposure — for example, exclude converters or website visitors in Demand Gen if Search/PMax is retargeting them.
• In remarketing, split lists into warm, hot, and cold to assign to different campaign types.

3. Use Campaign Priority Settings

• For Shopping: Set campaign priorities (low, medium, high) between Standard Shopping and PMax (if still using Standard).
• For Search campaigns, use bid adjustments and negative keywords to assert more control.

4. Labelling & Monitoring

• Label campaigns by funnel stage (Top, Mid, Bottom) and regularly monitor overlap in audience and performance.
• Use Google Ads Insights & Reports, including Search Term Insights, Asset Group Reporting in PMax, and Audience Overlap reports (in GA4) to detect duplication.

5. Granular Asset Grouping in PMax

• Create one asset group per product category/audience, rather than dumping everything into one PMax campaign.
• This gives better visibility and control, reducing cannibalization within the same campaign.

6. Geo or Time-Based Splitting

• Run campaigns targeting different regions or time slots if they’re meant to serve the same audience. For example, PMax during off-hours, Search during peak hours.

Example Use Case & Solution

Problem: You’re running a branded Search campaign, and after launching PMax, Search impressions and conversions drop.

Solution:

• Request Google Rep to exclude branded terms from PMax.
• Use exact match in the branded Search campaign.
• Analyse search term overlap using Search Term Insights in PMax.
• Separate brand and non-brand PMax campaigns if needed.

Summary Table

Cross-campaign cannibalisation can silently drain your ad budget and hurt results if left unmanaged. Whether you’re scaling an e-commerce store or an EdTech brand, the key lies in strategic audience segmentation, keyword control, and clear campaign intent.

Want to see how this works in practice?

Check out our Google Ads case study where we resolved major cannibalisation issues across Search, PMax, and Demand Gen for an EdTech company, leading to a 40% boost in branded traffic and a 28% drop in CPA.