D'Aloisio, who is described as a British-Australian entrepreneur, said he was "delighted" about the deal.
In a message on the Summly website, he wrote: "I am delighted to announce Summly has signed an agreement to be acquired by Yahoo.
"After spending some time on campus, I discovered that Yahoo has an inspirational goal to make people's daily routines entertaining and meaningful, and mobile will be a central part of that vision. For us, it's the perfect fit.
"When I founded Summly at 15, I would have never imagined being in this position so suddenly."
The Summly app will now be closed from the Apple store and its features integrated into Yahoo's mobile initiatives.
Yahoo has acquired several small mobile and web start-up companies since former Google executive Marissa Mayer became chief executive last year.
The Summly buy comes just two weeks after Google said it plans to retire its RSS reader application Google Reader on July 1.
The purchase has been seen by some as a bid to fill the gap left by Google Reader.
Summing up
17: Age of Nick D'Aloisio
15:His age when he founded the Summly app
$36.4-$72.8m: What Yahoo is believed to have paid for the app
9: The app's place on the free iPhone app chart last November
What it does
Automatically reduces lengthy online news stories and features into summaries
What he will do with his money
Buy a new computer and trainers, so he says
-Independent