The Sun reports that the Italian striker was asked for an autograph by the young fan at City's training ground, but turned the tables on the lad by asking him why he was playing truant from school.
The boy explained that he was absent because he was being bullied - sparking an incredible reaction from the 20-year-old superstar.
The City ace drove the boy and his mother to the school and demanded to speak to both the headmaster and the bully, during which he apparently mediated as the two boys buried their differences.
The unlikely knight in shining armour - who has hit the headlines all season for a string of on- and off-pitch controversies - then made the pair shake hands before he sped off in his Maserati.
"Mario feels strongly about bullying and thinks it's out of order, " a source told the paper.
"He had no qualms about sorting the mess out as he felt the lad should not be missing out on school."