Real Madrid had considered moving for Mourinho themselves and contacted Jorge Mendes about bringing him back.
But the super agent told them Mourinho was reluctant to return and that an agreement had been made with United in February.
An Inter Milan director confirmed last month that Mourinho was ready to take the United job.
Doorstepped by reporters as she left a restaurant following a meal with Mourinho, Bedy Moratti – sister of former club president Massimo Moratti – said: “We had a good time, he’s great. He’s missed as a person, but right now he’s happy, he’s going to Manchester.”