Performance Max now drives close to half of all Google Ads conversions, and for B2B SaaS accounts one specific failure mode explains a large share of its wasted spend: brand cannibalization. Left to its defaults, PMax bids on your own branded searches — your company name, your product name, and their variants — and reports the resulting conversions as its own. Those are the cheapest, highest-converting clicks in your entire account, and PMax harvesting them makes it look like a spectacularly efficient channel while it quietly spends budget on demand you already owned.
The mechanism is well documented. As one 2026 teardown of the problem in B2B SaaS accounts put it, branded search cannibalization inflates apparent ROAS by 15–30% and burns 8–15% of total PMax budget when it goes unchecked. This post explains why PMax does this by default, how to detect it in a B2B SaaS account where the symptoms hide inside blended reporting, and the exact fix — brand exclusions plus a dedicated brand campaign — that walls PMax off to the prospecting it is actually good at. If you are still deciding whether to run PMax at all, start with should B2B SaaS run Performance Max; this post assumes you are running it and want it to stop lying to you.
Why PMax eats your brand by default
Performance Max is a goal-seeking machine pointed at your conversion target across every Google surface — Search, Shopping, Display, YouTube, Gmail, Discover. When it looks for the cheapest path to a conversion, your own branded queries are the obvious answer: someone searching your exact product name is further down the funnel than any prospecting audience, clicks at a high rate, and converts cheaply. PMax has no built-in reason to leave that money on the table, so unless you tell it otherwise, it bids on brand and books those conversions. Nothing about this is a bug — it is the system doing exactly what you asked, optimizing for the lowest-cost conversion available.
The problem is attribution, not intent. Those branded conversions would overwhelmingly have happened anyway — through organic results, direct navigation, or a dedicated brand Search campaign. PMax taking credit for them tells you nothing about its ability to find new customers, which is the only reason to run an expensive automated prospecting channel. As one practitioner guide bluntly framed it, your PMax ROAS is a lie until you exclude brand — because the headline number blends cheap harvested demand with genuine prospecting and reports a flattering average that reflects neither honestly.
Why this is worse for B2B SaaS than ecommerce
Ecommerce brands feel brand cannibalization too, but B2B SaaS has a structural reason to care more: the whole channel-evaluation model rests on incremental pipeline, and branded conversions are the least incremental thing in the account. A demo request from someone who already searched your product name is not new demand — it is demand you generated through content, sales, word of mouth, or a prior campaign, now being re-credited to PMax. When that shows up as efficient acquisition, it corrupts the CAC math you use to allocate budget, the same distortion we unpack in cost per lead vs cost per SQL: a cheap blended cost per conversion hides an expensive true cost of acquiring a genuinely new customer.
The downstream damage compounds because Smart Bidding learns from what you feed it. If PMax's conversion data is dominated by high-converting branded traffic, the algorithm optimizes toward the profile of people who already know you — and spends less exploring the colder, harder prospecting audiences where real growth lives. So brand cannibalization is not just a reporting nuisance; it actively biases the machine away from acquisition. This is the same measurement-integrity argument behind honest ROAS for B2B SaaS: if the number you optimize toward is polluted, every decision built on it inherits the pollution.
How to detect it in your account
Because PMax reporting is deliberately opaque, you have to triangulate. Start with the search-terms insight and the brand-versus-non-brand breakdown Google now exposes for PMax, and look at how much of PMax's conversion volume carries branded intent. Then cross-reference: pull your brand Search campaign (if you run one) and your organic branded traffic, and check whether total branded conversions are roughly flat while PMax's share of them is climbing. If PMax's conversions rose but your brand campaign's impression share or your organic branded clicks fell by a similar amount, PMax is not creating demand — it is reallocating it to itself and charging you for the privilege.
A faster diagnostic: look at PMax's reported cost per conversion against your prospecting channels. If PMax's CPA is dramatically lower than every other new-customer source in the account, that is rarely because PMax found a magic prospecting vein — it is usually because branded traffic is dragging the average down. The rigor here is the same we apply in auditing Performance Max campaigns: never trust a PMax headline metric until you have separated the demand it captured from the demand it created. A suspiciously good PMax CPA in a brand-heavy SaaS account is a symptom, not a win.
The fix: brand exclusions plus a dedicated brand campaign
The remedy is two moves, done together. First, apply brand exclusions to Performance Max. As one setup guide describes it, you create a Brand List and apply it so PMax is blocked from serving on auctions where Google detects your brand. In the interface: build or select a Brand List (type your company and product names, confirm the matched brand entities), then apply it under the campaign's Additional Settings → Brand Exclusions. For own-brand prevention, do this at the account level through the shared library so every current and future PMax campaign inherits the exclusion rather than relying on you to remember it campaign by campaign.
Second, run a dedicated brand Search campaign to catch the branded traffic you just walled off from PMax. This is not optional cleanup — it is what makes the exclusion safe. A standalone brand campaign is cheap, controllable, and honestly measurable: you see exactly what branded defense costs and what it returns, without PMax's blended average obscuring it. Our guide to brand campaigns for B2B SaaS covers how to structure it. With brand excluded from PMax and captured by a dedicated campaign, PMax's numbers finally reflect only what it was hired to do — find new customers — and you can judge it on that basis alone.
What the numbers do after you fix it
Brace for PMax's reported performance to get worse, because it is finally telling the truth. Once brand is excluded, PMax loses its cheapest conversions, so its CPA rises and its ROAS falls — not because the campaign degraded, but because the flattering branded padding is gone. The right reaction is relief, not panic: you are now looking at PMax's real prospecting economics for the first time. Reset your expectations and targets to that honest baseline, and evaluate whether PMax's true cost of acquiring a new customer actually clears your bar, using the framework in should B2B SaaS run Performance Max.
You should also see budget reallocate toward genuine prospecting, which is the point. The 8–15% of spend that was harvesting owned demand now either funds real acquisition inside PMax or frees up for channels that actually expand your pipeline. Keep watching the brand-versus-non-brand split for a few weeks to confirm the exclusion is holding, and fold the fix into your wider signal hygiene — the same discipline behind tuning PMax search themes and audience signals. Clean inputs, honest attribution, and a channel judged on incremental customers rather than borrowed ones: that is what fixing brand cannibalization actually buys you.
The takeaway for B2B SaaS teams
Brand cannibalization is the most common reason a B2B SaaS Performance Max campaign looks like a star performer while contributing far less incremental pipeline than its numbers claim. The default behavior — PMax bidding on your own brand and booking the easy conversions — inflates ROAS by an estimated 15–30% and diverts a meaningful slice of budget away from the new-customer acquisition you are actually paying for. It is one of the few Google Ads problems with a clean, high-leverage fix that takes minutes to apply and pays off immediately in measurement integrity.
Exclude brand from PMax at the account level, run a dedicated brand Search campaign to catch that traffic honestly, and re-baseline PMax on the worse-but-true numbers that result. If you would rather have someone pressure-test whether cannibalization is inflating your account — and quantify how much prospecting budget it is quietly eating — our Google Ads audit separates the demand PMax captured from the demand it created, so you can judge the channel on the only metric that matters for SaaS: the cost of a genuinely new customer.