Rooney, the all-time leading goalscorer for Manchester United and the England national team and second in the English Premier League with
208 goals in 16 seasons, should make his MLS debut on July 14 when D.C. United plays its first match at Audi Field against the Vancouver Whitecaps.
Rooney, who is 32, signed what D.C. United described as a contract through the 2021 season. The Washington Post reported the last year of his contract is a option held by the MLS club.
He is not eligible to play until the secondary transfer window opens on July 10.
"It is fantastic to be joining D.C. United at such an exciting time in the club’s history with the new stadium opening in just a few weeks," Rooney, who was greeted by hundreds of fans when he arrived at the airport on Thursday, said in a statement. "Moving to America and MLS fulfills another career ambition for me. I have the hunger to be a success here and will give D.C. 100 percent - as I have always done for every team I have ever played for. When I visited earlier this summer I was really impressed with everyone I met connected with the club, and of course the new Audi Field. Now I can’t wait to get on the pitch in a United shirt and join my new teammates to bring success to this club."