The Pew Research Center survey also found the younger adults were much more likely to have heard about the video through social media than traditional news sources.
The video, which has been viewed more than 100 million times online, calls for the arrest of Ugandan rebel leader Joseph Kony.
The video, by the San Diego-based non-profit group Invisible Children, focuses on Kony's brutal tactics in northern Uganda over two decades that resulted in thousands of deaths and kidnappings of children forced to become soldiers in his Lord's Resistance Army.
The Pew survey shows that in a three-day span after the release of the video, 58 percent of adults ages 18-29 said they had heard about the video, including 40 percent who said they heard a lot about it. By contrast, among those ages 30-49, 20 percent said they had heard about the video, while among those 50-64, 18 percent had heard about it and among those 65 and older, 19 percent.
The survey also found young adults were more than twice as likely as older adults to have watched the video on YouTube or Vimeo.
"Kony 2012" is one of the most viewed videos ever on YouTube and Vimeo.
The survey is based on telephone interviews March 9-11 with 814 Americans age 18 or over. It has a sampling error of 4 percentage points.