Dr Kawashima's Brain Training for the popular Nintendo DS portable console encourages users to perform mental arithmetic and language tests and can "help you train your brain in just a few minutes a day", according to Nintendo's website.
But Which? said scientists examining the claim that it can improve your memory found that there was no evidence that it can achieve "any functional impact on your life whatsoever".
Which? Editor Martyn Hocking said: "If people enjoy using these games, then they should continue to do so - that's a no-brainer. But if people are under the illusion that these devices are scientifically proven to keep their minds in shape, they need to think again."
Brain Training, promoted by the likes of Nicole Kidman, Patrick Stewart and Julie Walters, has sold more than 90m units worldwide since, and a new version of the game for Nintendo's second-generation DSi console is set for release in April.
However, the title was not the only brain training game highlighted by Which? researchers as failing to live up to its billing. The magazine said similarly weak evidence was found by experts for claims made by Mindfit by Mindweavers, Test and Improve Your Memory by Focus Multimedia, Lumosity by Lumos Labs and Mind Spa by A/V Stim.
Click below to see the Nintendo DS-i in action on PCA TV: