- Khvicha Kvaratskhelia (47' Pen)
- Victor Osimhen (68', 73')
Osimhen could have doubled the visitors' lead in the 61st minute but his effort was ruled out for a foul on Spezia defender Mattia Caldara.
The Nigerian netted seven minutes later, however, with a close-range header following a mistake by Spezia defender Ethan Ampadu.
Another error by the Spezia defence gifted Osimhen the chance to make it 3-0 in the 73rd minute with his 16th league goal of the season, a personal record.
Napoli provisionally increased their advantage over second-placed Inter Milan to 16 points. Spezia remained 17th, hovering five points above the relegation zone.
- Marco Di Bello