EU Home Affairs Commissioner Cecilia Malmstrom and Justice Commissioner Viviane Reding secured the agreement from US Attorney General Eric Holder after talks with the American official in Dublin, Malmstrom said.
"Agreed with the US in Dublin to set up a transatlantic expert group to receive more info on PRISM and look at the safeguards," Malmstrom said on Twitter, without elaborating.
An EU source said the United States had given Brussels details about the PRISM programme and also about the legal aspects of the surveillance scheme.
The move comes days after the EU demanded answers from Holder and warned of a "grave" threat to the rights of European citizens from the intelligence programme.
Details about PRISM were leaked by former US security consultant Edward Snowden and revealed by The Guardian and Washington Post last week.
The top-secret intelligence dragnet operated by the US National Security Agency (NSA) collects and analyses data from Internet and phone users around the world.