Right Media shareholders will be paid approximately equal parts cash and stock, and Right Media options and similar equity awards will be assumed by Yahoo!
Terry Semel, chairman and chief executive of Yahoo!, said: "The acquisition of Right Media will further Yahoo!'s goal to create the industry's most open, accessible and vibrant advertising marketplace, which will help democratise the buying and selling of digitally enabled advertising."
"This acquisition is an important step in our long term vision to build the industry's leading advertising and publisher ecosystem. We believe that Yahoo!'s open approach is a clear differentiator from others in the industry and provides significant benefits to advertisers, publishers and Yahoo! itself."
The Right Media Exchange is the industry's largest emerging online advertising exchange, and as publishers turn to exchanges to generate revenues for their ad inventory, this acquisition will help Yahoo! establish a leading position in this large segment of the online ad market.
Michael Walrath, chief executive and founder of Right Media, said: "We share Yahoo's vision of a more empowered marketplace, where efficiency, transparency and accountability in online advertising become the norm. We are very excited by the prospect of becoming part of Yahoo! as it looks to revolutionise the media buying and selling landscape."
This news comes merely weeks after Google bought online ad delivery company DoubleClick for £1.5bn, beating competition from Microsoft and Yahoo!. Google now faces a possible investigation after rivals claimed the acquisition would create a monopoly in online ad sales.