Once embedded within the game, developers will collect revenues from the ads on both cost-per-impression and cost-per-click scales. The revenues will be divided between Google and the game's publisher.
"With this program, advertisers can now reach the growing number of gamers who are engaged in online play," the company said in a statement.
"For instance, in anticipation of a sporting event, an advertiser can use the technology of AdSense for Games to feature its logo within that sports event's accompanying online game and reach its relevant demographic as a result."
Among the developers participating in the beta are Konami, Playfish and Mochi Media. Early advertisers include Sony Pictures, Sprint and online insurance house Esurance.
The placement of ads within games has long been viewed an untapped and potentially lucrative market for ad networks. In 2006, Microsoft was rumored to have paid hundreds of millions of dollars for Massive Inc., while Sony launched its in-game ad programme earlier this year.
Google indicated its interest in the market last year when it acquired AdScape media.