Google Inc said it will allow some Google Play users to see advertisements for apps in the coming weeks.
Users will see ads from a pilot group of app developers who are already running ads on Google search, the company said in a blog post.
Google's advertising revenue has come under pressure as more consumers access its services on smartphones and tablets, where ad rates are typically lower.
The growing popularity of mobile devices has made Facebook Inc a greater threat in the battle for advertisers. The social network reported in January that mobile ads on its network doubled in the fourth quarter.
Google's shares were up about 2 percent at $557.16 in afternoon trading.