The company labelled the ad for the website, called CougarLife, which promotes relationships between older women and younger men, as "non family safe".
However it allows ads that publicise such liaisons between older men and younger women - from a website called ArrangementSeekers.
Both CougarLife and ArrangementSeekers are owned by the same company, Avid Life Media.
Google officials then refused to allow the advertisements for the Canadian-owned dating service, which introduced "women in their prime with younger men", to be sent to third party websites.
A "cougar" is a slang term used for such women in the US and is epitomised by celebrities such as Demi Moore, whose husband, Ashton Kutcher, is 16 years her junior.
According to The Telegraph, the company said the campaign, which cost 100,000 US dollars a month, generated referrals that accounted for almost two thirds of its traffic.
Google's decision to censor the ad only landed it in more trouble as critics began accusing it of hypocrisy and sexism.
Claudia Opdenkelder, who is the founder of the CougarLife, and whose partner is 14 years her junior, accused the search giant of sexism.
"It's just wrong all around," The Telegraph quoted her as telling The New York Times.
"It's age and gender discrimination. It's just about older, successful, independent, strong women who enjoy someone that's younger."
She added to Canada's National Post, "It's a huge double standard and I think women should just be appalled.
"We just want to be treated the same way as all the others, and the discrimination against the word 'cougar' makes it even worse.
"It makes us - cougar women - feel like dirty perverts."
A Google spokeswoman denied all the accusations.
She said the company had a list of words, which trigger a review of the site and the ads before a decision is made but declined to say if the word "cougar" was one of them.
"It's not just about the ad, it's about the ad and the landing page of the site," she said.
"Anything that's considered non-family safe will not run on the Google content network at this point."