Yahoo did not disclose the financial terms of its acquisition of OnTheAir, but said the team would be joining Yahoo's mobile group.
A Yahoo spokeswoman said that Yahoo had not plans to offer OnTheAir's existing product, which lets Web users host live video conversations and was launched in March.
The deal marks the second small, mobile-oriented deal since Mayer became CEO earlier this year. In October, Yahoo acquired Stamped, a New York-based mobile startup that allows consumers to share information about favorite restaurants and music on their smartphones.
Mayer, a former Google executive, has said that her top priority is to create a coherent mobile strategy for Yahoo and that she intends for at least half of the company's technical workforce to be working on mobile products.
Shares of Yahoo were up 1.5 percent at $18.82 in trading on Tuesday.