The 21-year-old saw his effort in the 93rd minute deflect over Michael Agazzi after the game appeared to be heading for a draw.
Victor Ibarbo had put the visitors ahead early in the first half before David Astori inadvertently turned the ball into his own net.
Edinson Cavani then fired Napoli in front midway through the second half from close range before Marco Sau looked to have secured a point for Ivo Pulga’s side.
Napoli were the dominant of the two sides in the opening exchanges as Goran Pandev fired over from 18 yards following some good link up play with Marek Hamsik.
Radja Nainggolan then sliced his shot wide of the goal before Ibarbo capitalised on a poor Cavani clearance to smash past Antonio Rosati from 20 yards.
The hosts continued to dominate as Blerim Dzemaili twice went close, while Cavani’s audacious overhead kick flew over the bar as Cagliari took the one goal advantage into the interval.
Napoli began the second half in a similar vein and were rewarded five minutes after the restart when Astori turned past Agazzi following a well worked free kick involving Pandev and Hamsik.
The Cagliari goalkeeper then denied Cavani as Napoli upped the pressure on the visitors, before the Uruguayan fired his side in front in the 64th minute after Agazzi had palmed Paolo Cannavaro’s effort into the path of the 26-year-old striker.
Sau was introduced three minutes after the goal and drew the visitor’s level with 20 minutes to go after the Italian capitalised on some poor defending from Cavani and Valon Behrami to curl his effort past Rosati into the top corner from the edge of the Napoli 18 yard box.
The Partenopei went in hunt for the winner and were duly rewarded in the 93rd when Insigne cut onto his right foot and saw his effort loop over Agazzi after his shot took a wicked deflection off Gabriele Perico and into the far corner.
The win sees Napoli move seven points clear of AC Milan and strengthens their grip on a Champions League place, while Cagliari remain in 10th in Serie A.
- Sports & Recreation
- Michael Agazzi
- Edinson Cavani