Napoli held on to their early lead of Serie A after Sunday's goalless draw at Fiorentina, while Atalanta's 1-0 win at Verona ensured they moved level with the early pacesetters.
Luciano Spalletti's Napoli were less flamboyant than in their opening two victories but had marginally the better of the opportunities in a lively encounter at the Stadio Artemio Franchi.
Not even the introduction in the second half of lively new signings Giacomo Raspadori, Giovanni Simeone and Tanguy Ndombele could push the away side to the win.
The stalemate puts Napoli on seven points from their opening three matches, level with several teams, including champions AC Milan and Atalanta.
Fiorentina, who are also unbeaten, sit ninth on five points.
An intense contest in Florence began with the hosts on the front foot and they went closest to taking the lead midway through the first half when after Alex Meret spilled Riccardo Sottil's shot, Giacomo Bonaventura flashed a low drive just wide.
Victor Osimhen had a tap-in ruled out for offside just before the break as Napoli grew into the game. The away side should have been ahead not long after the restart.
Amir Rrahmani headed Piotr Zielinski's cross narrowly over in the 48th minute. Then, just after the hour mark, Hirving Lozano wasted a golden chance to put Napoli ahead.
Khvicha Kvaratskhelia, in less eye-catching form than in his first two games, dangled the most inviting of crosses from the right which Mexico attacker Lozano somehow headed wide close range.
Raspadori came on after an hour and was denied the winner with eight minutes of his debut remaining, Pierluigi Gollini getting down well to push the Italy international's low shot wide.
Earlier Teun Koopmeiners drilled home a powerful winner four minutes after half-time at the Stadio Bentegodi to keep Atalanta unbeaten.