Pirlo's goal was entirely worthy of the hallowed Maracana, which provided the perfect stage as he became the fifth Italian to reach a century of full internationals.
The 34-year-old brought the fickle and notoriously difficult-to-please Maracana crowd to its feet as he curled the ball over the wall and into the top corner in the 27th minute from distance.
The crowd chanted Pirlo's name before and after the goal, the rarest honour for a foreign player on a stage previously graced by the likes of Garrincha, Pele, Zico and Romario.
"I don't have words to describe Pirlo, he's an example to everyone," Italy coach Cesare Prandelli told reporters.
Balotelli's goal was more about power as he latched on to Emanuele Giaccherini's flicked pass, barged past defender Francisco Rodriguez and fired the ball past Jose Corona with 12 minutes to go.
Javier Hernandez had replied for Mexico with a penalty seven minutes after Pirlo's masterpiece.
Balotelli, whose notorious temper had been bubbling under the surface for most of the second half, took his shirt off in celebration, earning a yellow card and a reprimand from his coach.
"He wanted to take his shirt off and show his muscles, but all the yellow cards count," said Prandelli, who has previously suspended Balotelli for indiscipline with former club Manchester City.
"But he played well and didn't let anyone get to him. He was attentive for the whole game and has shown strength of character."
Balotelli said he did not realise that he was not allowed to take off his shirt.
"I didn't know the rules, I won't do it again," he told Italian media.
The defeat heaped more pressure on Mexico's under-fire coach Jose Manuel de la Torre, whose team have been held to draws at home by Costa Rica, Jamaica and the United States in World Cup qualifying.
RIOT POLICE
The match was again played against the backdrop of teargas and rubber bullets as riot police confronted protesters outside the Maracana stadium.
A similar demonstration had marred Saturday's opening match between hosts Brazil and Japan in Brasilia. The protests are against the amount of public money being spent on staging the event and next year's World Cup.
Balotelli had a couple of early chances for Italy while Mexico's Andres Guardado shaved the crossbar after mistake by Ignazio Abete in a lively start to the Group A encounter.
Pirlo, always at the heart of the action, had a penalty turned down before bringing the Maracana to its feet with his 27th-minute goal.
Mexico levelled seven minutes later when Andrea Barzagli was dispossessed by Giovani dos Santos and then barged over the Mexican forward. Hernandez sent Gianluigi Buffon the wrong way from the penalty spot.
Pirlo then produced an outrageous reverse pass to release Abete on the right, the move ending when Balotelli's effort was blocked by Corona.
