Victor Osimhen netted his third goal of the season from the penalty spot 15 minutes into Napoli's first home match since lifting the league title in front of their fans for the third time back in June.
And captain Giovanni Di Lorenzo made sure Napoli would make it six points from six in the 64th minute, not long after Maxime Lopez was sent off and Giacomo Raspadori -- who had hit the post seconds after kick-off -- blasted a penalty into the stands.
"I think we played well, kept hold of the ball, we're happy to have won the match in front of our fans," said Di Lorenzo.
"We played well as a team. We've started well and the attitude is right so we've got everything for us to have a good season."
Di Lorenzo's first goal of the campaign came after some magical play from the returning Khvicha Kvaratskhelia, who made his season debut an hour into a one-sided contest at the Stadio Diego Armando Maradona.
The Georgian was surrounded by defenders near the penalty area but took a couple of steps forward before slipping in Di Lorenzo for a simple low finish.
It's early days but Napoli already look a dangerous proposition under new coach Rudi Garcia, who has a tough act to follow in new Italy boss Luciano Spalletti, the architect of the Scudetto triumph.
Lazio finished second last season but were seen off at home thanks to Italy forward Mateo Retegui's first Serie A goal after signing from Boca Juniors this summer.
It was a good sign for Spalletti who will need goals when Italy face North Macedonia and Ukraine in Euro 2024 qualifying next month.
- Bologna penalty fury -
Outraged Bologna held Juventus in Turin but were left wondering what might have been after being denied what looked to be a clear penalty moments before Dusan Vlahovic salvaged a point for the underwhelming hosts.
Vlahovic headed Juve level with 10 minutes remaining at the Allianz Stadium after Lewis Ferguson had put Bologna deservedly ahead midway through the first half.
But Bologna were incredulous when after on-field and VAR officials failed to punish Samuel Iling-Junior -- who subsequently set up Vlahovic's equaliser -- for cutting down Dan Ndoye and stopping him from tapping in from close range.
It was a decision which so angered Bologna that it prompted a livid post-match reaction from the club's CEO Claudio Fenucci as coach Thiago Motta refused to talk to media.
"I've done this job for 25 years and I don't often go on TV to talk about referees," said Fenucci.
"The win was taken from us by an incredible refereeing decision... It's unthinkable that a challenge like that is not punished with a penalty and a red card."
Not even the return of Paul Pogba to midfield after a year of injury problems could inspire Juve to claim the three points, the France star doing little as a second half substitute as Juve huffed and puffed ineffectively.
It was an uninspiring display from Juve which poured cold water on the idea that they are back as league title contenders.
"I'm obviously happy to be back... but I'm also a bit disappointed with the result," said Pogba to DAZN.
"The positive thing is that we didn't lose."