The hosts started strongly and were ahead after just six minutes.
Mattia Zaccagni’s free-kick was well-saved by Alex Meret, but from the resulting corner, the ball fell kindly to Gustav Isaksen, who rifled an unstoppable effort into the top corner.
However, Napoli were level just a few minutes later with their only shot of the first half. Giacomo Raspadori latched onto Romelu Lukaku’s pass, before cutting inside and striking into the back of the net.
That goal seemingly angered Lazio, who dominated the rest of the half.
Taty Castellanos struck just wide from mid-range and unfortunately had to come off injured afterwards. Nicolo Rovella also tested Meret from the edge of the box, but the score remained level at half-time.
Antonio Conte clearly got into his players in the dressing room as Napoli came out much better at the start of the second half, with Lukaku trying his luck from the edge of the area and forcing an early save from Ivan Provedel.
Their pressure eventually paid off as Adam Marusic, unfortunately, diverted the ball into his own net after trying to intercept a pass.
Zaccagni then thought he equalised for Lazio just three minutes later against the run of play, but it was ruled out for offside.
Marco Baroni’s men pushed for a late leveller, and in the 87th minute, Boulaye Dia sent the home crowd wild as his strike from the edge of the box went in off the post.
It was a body blow for Napoli, who despite stretching their unbeaten away league record to 12 games, opened the door for Inter Milan to potentially overtake them at the top of the table.
Meanwhile, Lazio are looking over their shoulders themselves, as despite earning a well-fought point, they could drop out of the top four if Juventus win this weekend.
Flashscore Man of the Match: Boulaye Dia (Lazio)