Blunt and McGregor previously worked together on the 2011 film "Salmon Fishing in the Yemen."
Jim Bell, the executive producer of NBC's coverage of the games, announced the stars' participation in NBC coverage of Friday's 4 1/2-hour Olympics opening ceremony during a teleconference with journalists Thursday, EW.com reported.
"It is pretty breathtaking," Bell said.
"I think it will give you a sense of the flavor of our coverage and the feeling we're all having going into these games," EW.com said Bell added. "Having seen it ... I can tell you that it includes some amazing moments, including one that I think will be among the most astonishing and memorable in opening-ceremony history, and one that people will be talking about for years to come."