Dentsu becomes a ChatGPT ad pioneer — and hands UK brands an AI-search edge
Updated: Aug 19
Dentsu, one of OpenAI's four UK agency launch partners for advertising in ChatGPT, has partnered with Adthena to help British brands compete in an unpredictable new AI-search auction where cost-per-click has swung between 39% and 278% with no visible cause.
Advertising moves inside the AI assistant
The search box is no longer the only front door to a purchase. With ads now live inside ChatGPT, the UK arm of Dentsu has positioned itself as an early mover — one of just four UK agency launch partners for OpenAI's advertising, announced on 23 July 2026.
Dentsu is not theorising. It has already run live campaigns for brands including Hilton, and says three of its clients rank among the top nine ChatGPT advertisers in the UK. In a channel this young, that experience is itself a competitive asset.
Toby Benjamin, Chief Media Officer at Dentsu UK & Ireland, put the stakes simply: 'ChatGPT is already changing how consumers research, compare, and make purchasing decisions.'
A brand-new auction with brand-new chaos
The catch is instability. When ChatGPT's ad auction opened, brands saw cost-per-click swing between 39% and 278% with no visible explanation — the kind of volatility that makes budgets impossible to plan and easy to waste.
That is the gap Dentsu's tie-up with Adthena targets. Adthena's new Decision Intelligence product monitors ChatGPT placements to spot when competitors enter, how their timing moves auction prices, and where budget is being inflated.
The practical output is advice a media buyer can act on: cap bids in over-heated categories, or redirect spend toward uncontested prompt segments. In other words, bring the discipline of mature search to an immature channel before rivals do.
Why UK marketers should care now
ChatGPT ads only opened on 6 June 2026, with self-service access following on 22 June. That means the field is still thin — a narrow window where early, well-managed spend can buy visibility cheaply before the auction fills up and prices settle higher.
It also reframes 'AI search' from a scary threat into a live media channel. Brands have spent 18 months worrying about whether AI assistants would mention them. Now the question is whether they should be paying to appear — and how to measure it.
The uncomfortable truth: the brands learning this auction in 2026 will hold a structural cost advantage over those who wait until it is 'proven' in 2027.
Marketing Minute's take: treat it as an experiment budget, not a leap of faith
We would not pour a core budget into ChatGPT ads yet. But we would carve out a disciplined test — a fixed sum, clear conversion tracking, and a hard rule to pause when CPCs spike beyond a set ceiling.
The Dentsu-Adthena model matters less for the specific tools and more for the principle: in any new channel, the winners are the ones who instrument it early, learn the auction's quirks, and cap their downside while the upside is cheap.
Quick FAQ
Can brands advertise inside ChatGPT now?
Yes. Ads in ChatGPT opened on 6 June 2026, with self-service access from 22 June. Dentsu is one of four UK agency launch partners for OpenAI's advertising and has already run live campaigns for brands including Hilton.
Why are ChatGPT ad prices so unpredictable?
Because the auction is new and thinly populated, cost-per-click has swung between 39% and 278% with little visible cause. Adthena's Decision Intelligence aims to reveal competitor activity and auction dynamics so buyers can cap bids or shift budget.
Should UK SMEs invest in ChatGPT advertising in 2026?
Cautiously. A small, well-tracked test budget with a firm CPC ceiling lets brands learn the channel cheaply while it is uncontested, without betting core spend on an unproven, volatile auction.
AI search stopped being a threat and became a media channel the moment ads went live inside ChatGPT. The brands that instrument it now — with tight tracking and a hard CPC ceiling — will learn its quirks cheaply. The rest will pay premium prices to catch up in 2027.
— Dimitro Cohen, Technology & Ad-Tech Correspondent at Marketing Minute
Takeaway: advertising inside AI assistants is real. Run a small, tightly measured test now rather than waiting for the auction to mature and prices to rise.
If a customer asks ChatGPT to compare your category tomorrow, would your brand show up — organically or as an ad?
If you would like to know more about this topic, please contact us on danieln@merxmarketing.co.uk
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Written by Dimitro Cohen, Technology & Ad-Tech Correspondent at Marketing Minute
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