Although the relegation-battling Winged Lions were unbeaten in their last three matches, the Partenopei were firm favourites to come out on top.
And they were very much the dominant side in the first half, as Amir Rrahmani saw his close-range effort saved by Filip Stanković with just four minutes on the clock, before Khvicha Kvaratshkelia and John Yeboah were both denied by the Serbian stopper.
Having had the visitors under constant pressure, Napoli were awarded a penalty nine minutes before HT when Mathías Olivera’s effort was handled by Jay Idzes. However, Romelu Lukaku saw his spot-kick saved low down to his left by Stanković.
Antonio Conte’s side had another great chance to go in front three minutes later when a ball across the box found André-Frank Zambo Anguissa unmarked, but the midfielder – who had scored in both of his last two games – blazed his first-time effort over the crossbar.
In eventually reaching the interval with the scores at 0-0, Venezia had achieved one of their more pressing objectives, but with Napoli unbeaten in 13 Serie A games against newly-promoted opposition, they would need a touch of sheer genius to pull off a near-miraculous win.
Eusebio Di Francesco’s men continued keeping Napoli at bay in the early stages of the second half, and indeed should have gone ahead when Hans Nicolussi Caviglia’s inswinging free-kick from the byline needed to be dealt with by Meret, who pushed the ball over the bar.
As ever, Lukaku continued to be the home side’s focal point, and he came agonisingly close to an opener just after the hour mark, when he broke into the area and unleashed a shot which beat Stanković but came back off the right post.
With Napoli sustaining wave after wave of attack, their efforts eventually paid off with 11 minutes remaining, when Raspadori pounced on a loose ball inside the area and fired it into the bottom right-hand corner of the net, breaking Venezia hearts and sending the home fans wild.
This late intervention proved decisive, as Conte’s men held on for a victory which lifts them above Inter Milan and into second place for the time being. Venezia, meanwhile, remain 19th and very much in trouble heading into the New Year.