Now 37, Lewandowski was with Borussia Dortmund at the time and was eager to move to Old Trafford, but his German club refused to do business.
He recalled to BBC Sport: "To Manchester United I decided and said yes. I wanted to join Manchester United, to see Alex Ferguson.
"They (Dortmund) could not sell me," Lewandowski added. "Because they knew if I stayed they could earn more money, and that I could wait maybe one or two more years.
"But it is true that I said yes to Manchester United."
Lewandowski also said: "Maybe it could be a regret (not to play in the Premier League).
"But when I am looking back (having) played for Bayern Munich, Dortmund and now Barcelona I have to say I am very happy with my career.
"I don't have this kind of feeling that I missed something, because every move or decision... I made because I wanted it."