Mourinho, who challenged United's domestic dominance while at Chelsea between 2004-2007, was speaking Real's their Champions League semi-final against Borussia Dortmund.
Real eliminated United in the last 16.
"What he did is what he has been doing all his life, winning," Mourinho told reporters. "Sometimes not consecutively because it is impossible to do it."
United clinched their 20th league title on Monday with a 3-0 win over Aston Villa, giving Ferguson the 49th trophy in his long managerial career.
"That's his life and his career. I congratulate him, it is not a surprise to me or to the world that Sir Alex and Manchester United won the title again," said the Portuguese coach.
Mourinho led Chelsea to Premier League titles in 2005 and 2006, breaking United's stranglehold on the competition.
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