Sega Sammy Holdings will pay €706m (£625m / $776m) in the deal, with talks being confirmed at the weekend. When trading closed on Friday, Rovio's stock market value was $707m (£571m).
Rovio's most famous product, Angry Birds, launched in 2009 and is reported to be the first mobile game to pass a billion downloads. It has spawned sequels, merchandise and two Hollywood movies – but Rovio has struggled to recreate the same impact with any of its other titles, which led to talk of a sale materialising.
Rovio – which has around 550 staff worldwide – announced earlier this year that it was reviewing its business and had held talks over selling up to a larger entity. Israeli rival Playtika emerged as a potential buyer, but talks came to nothing.