Seedorf's Milan needed a late Mario Balotelli penalty to beat Verona 1-0 at San Siro.
Balotelli slotted to the left of Verona goalkeeper Rafael from the spot in the 82nd minute, after Alejandro Gonzalez clumsily fouled Kaka.
Kaka was not threatening the goal, running towards the byline, but Gonzalez slid in and brought the Brazilian down, with Balotelli's calm conversion giving Seedorf three points in the first match of his managerial career.
Seedorf – who spent a decade as a player at the Serie A giants from 2002 to 2012 – was appointed this week to replace the sacked Massimiliano Allegri, and would have been frustrated as Robinho's second-half shot deflected onto the post with Rafael well beaten.
Balotelli also spurned a host of chances, but eventually made amends as Milan climbed to 11th in the table.
Napoli were hurt by a late equaliser at Bologna, as Rolando Bianchi's stoppage-time strike rescued a 2-2 draw for the 10-man hosts.
Bianchi opened the scoring in the 37th minute, converting Alessandro Diamanti's assist, but Napoli flexed their muscle after the break.
Gonzalo Higuain's penalty levelled proceedings in the 62nd minute, before Jose Callejon struck with 10 minutes to play.
Bologna's Panagiotis Kone was sent off for a second bookable offence in the 84th minute, but Bianchi was still able to claim a crucial point for his struggling side.
Fourth-placed Fiorentina are just three points behind Napoli after a comfortable 3-0 win at rock-bottom Catania.
Debutant Alessandro Matri, signed on loan from Milan this week, laid on the first goal for Matias Fernandez and then added two goals of his own as Vincenzo Montella's side extended their unbeaten streak to seven.
Inter's poor start to 2014 continued as their winless run stretched to four with a 1-0 defeat at Genoa.
Walter Mazzarri's side were knocked out of the Coppa Italia last week at Udinese and disappointed on the road once more against 10th-placed Genoa.
Luca Antonelli headed home a corner with seven minutes remaining, enabling Gian Piero Gasperini to celebrate victory against his former charges for the first time.
A 2-1 win at Chievo represented Parma's third Serie A success in a row, with Alessandro Lucarelli scoring the winner in the 93rd minute.
Lazio also sealed an away win with a stoppage-time goal, as Hernanes' late effort wrapped up a 3-2 victory at Udinese.
Lazio trailed twice but an Andrea Lazzari own goal pulled them level with eight minutes left and there was still time for Hernanes to shock the hosts.
Other results saw Torino win 2-0 at Sassuolo while Atalanta edged Cagliari 1-0.
