United secured their 20th league crown with a 3-0 win over Aston Villa on Monday, but Mourinho has admitted that he was not surprised that the club regained the title this season.
"What Ferguson did this season is what he has done all his life - winning," Mourinho told reporters at a press conference.
"Sometimes it's not consecutively, because that would be impossible, but his career has been that - to win.
"I want to congratulate him but it is not a surprise to me or to United fans that Ferguson is champion again."
Mourinho is reportedly the favourite to replace Ferguson at United when the Scot retires.