The teenager was seeking an easier way to read news stories and other content on the smaller screens of smartphones, so he built an app for that.
The deal announced Monday is Yahoo's fifth small acquisition in the past five months. It's part of CEO Marissa Mayer's effort to attract more engineers with expertise in building services for smartphones and tablet computers, an area of technology that she believed the Internet company had been neglecting.
Yahoo didn't disclose how much it is paying for Summly.
Founder Nick D'Aloisio began working on the app at his London home when he was 15. He's younger than Yahoo, which was incorporated in March 1995.
D'Aloisio said Summly will no longer be available, but the technology will return in other Yahoo products.