Mourinho, who prior to his dismissal from Chelsea this season had said he was more "serene" than ever, seems to have flown into a rage when his 11-year-old daughter told him about playground taunts that another boy had made, comparing her with her father.
Mourinho went into the playground at the £6,500-a-year school his daughter attends in Setubal, near Lisbon, on Wednesday afternoon and found the boy who had been taunting his daughter, Matilde.
He then appears to have pulled the 12-year-old boy by the ears and gave him a thorough dressing down, as other parents and pupils looked on in bemusement. It is not clear whether he employed the "hairdryer" technique favoured by his former rival, Sir Alex Ferguson.
One witness told the Portuguese newspaper Correio da Manha that he was left "speechless" as he watched Mourinho scold Pedro Antonio.
Mourinho, 44, was then hauled into the office of the headmistress like a naughty schoolboy and made to apologise to his tearful victim and his family.
Isabal Simao, the headmistress of St Peter's school, said Mourinho appeared truly embarrassed and later wrote to the boy and the school to apologise for his behaviour.