The Brazilian powerfully headed home a cross from compatriot Kaka in the 36th minute as Jose Mourinho tasted his first defeat as Inter boss.
The Nerazzurri finished the game with 10 men after Nicolas Burdisso was sent off in the 77th minute, while Marco Materazzi was also sent to the stands from the Inter bench for protesting too strongly in a fiery end to the derby.
Carlo Ancelotti’s side look to have banished their woeful early-season form though after their third straight win lifted them up to sixth in the Serie A table.
Inter’s first defeat of the season leaves them fourth, two points behind leaders Lazio.
Mauro Zarate was once again the star of the show in the Biancocelesti’s 3-1 victory in Torino, although the match ended on a sour note as the hosts were reduced to nine men in a stormy finish.
Zarate set up Goran Pandev’s opener after half an hour and then doubled Lazio’s lead soon after the hour mark.
With less than 10 minutes to go, Matteo Sereni saw red for bringing down Christian Brocchi in the box, and Zarate stepped up to score Lazio’s third from the penalty spot.
Francesco Pratali also saw red for Torino before Nicola Amoruso got them a consolation goal from the spot, but home coach Gianni De Biasi was not around to see it after being sent from the sidelines as tempers flared.
Napoli lie a surprise second, one point off the pace, after a late strike from substitute German Denis maintained their unbeaten start to the season and inflicted a fourth successive defeat on Bologna.
The Argentinian forward broke the deadlock with just three minutes left on the clock to snatch the spoils for the visitors.
Simone Pepe struck his second goal of the week to help Udinese claim a 2-1 victory over Siena which lifted them up to third.
Fabio Quagliarella opened the scoring after 22 minutes on his return to the first team before Pepe doubled his side’s advantage seven minutes later.
And the 25-year-old midfielder’s strike would prove to be decisive as Houssine Kharja grabbed a goal back for Siena after 38 minutes, but it was not enough.
Catania gave further evidence they could be the surprise package in Serie A this season by moving into the top five with victory over Chievo.
Michele Paolucci scored the only goal of the game to earn the hosts their third 1-0 win of the season and extend their 100 per cent home record.
Chievo finished the game with 10 men after Davide Mandelli was sent off five minutes from time, and find themselves hovering just a point above the bottom three.
Roma recovered from their midweek defeat at Genoa with a 2-0 win over Atalanta at the Stadio Olimpico.
The Giallorossi’s second win of the season was sealed by first-half goals from Christian Panucci and Mirko Vucinic.
Davide Ballardini’s promising start to life as Palermo coach continued as Fabrizio Miccoli’s second-half strike prolonged Reggina’s dismal early-season form.
The former Italy international struck after 52 minutes to seal a 1-0 win for the hosts and condemn Reggina to their fourth defeat in their opening five fixtures.
And Lecce piled the misery on Cagliari and their coach Massimiliano Allegri as they ran out 2-0 winners.
Goals in either half from Guillermo Giacomazzi and Jose Castillo left Cagliari without a single point to show from their five games so far this season.
On Saturday Fiorentina defeated Genoa 1-0 on Saturday evening to get their Serie A campaign back on track after their midweek mauling at the hands of Lazio.
Summer signing Alberto Gilardino again proved his value to his new employers as his second-half goal handed the Viola their second win of the season while condemning Genoa to a third away defeat.
Meanwhile in Saturday’s other game, Sampdoria were left still searching for their first win of the season after being held to a goalless draw at home to Juventus.
The closest either side came to scoring in a cagey game was when Alessandro Del Piero hit the outside of the post for Juve in the 20th minute.
The point lifts the Bianconeri above Napoli into a share of second place with Lazio and Atalanta, but was not enough to threaten Inter Milan’s lead at the top of Serie A.