Mourinho, who managed Rooney at Old Trafford for one season before his short-term return to Everton, expects the 32-year-old to further raise the profile of the sport in the United States.
"When he made it at Everton, his boyhood club, the world was surprised with that kid and then he went to Manchester United and he had the incredible career he had," The Sun quotes him as saying.
"Then in the Premier League again at Everton Football Club, so I think his career in England was perfect. He decides the MLS [is next] and in MLS, you have always some iconic players that are going to end their career there.
"You had Gerrard, you had Lampard, you had [Patrick] Vieira, you had so many of them. David Beckham played there, too. You now have Zlatan [Ibrahimovic], you now have Wayne.
"I just hope he enjoys it and, of course, he'll bring the attention that the MLS needs to attract more people, to steal some people from the other sports that normally the American people are in love with."
Rooney is due to be unveiled by DC United early next week and is in line to make his debut on July 14.