Lorenzo Insigne gave Napoli a ninth-minute lead before Mertens opened his account, placing a low shot past Ivan Provedal into the far corner from just outside the penalty area in the 38th minute.
Francesco Caputo pulled one back just before the hour for Empoli only for Mertens to strike again, this time stroking a nonchalant effort over Provedal from the edge of the area.
It was Mertens's 74th league goal for Napoli, overhauling Careca's total to make him the club's fifth highest all-time scorer in Serie A.
Substitute Arkadiusz Milik added a fourth before Mertens completed his hat-trick, rounding Provedal to score into an empty net after the Empoli goalkeeper rushed out of his penalty area to try to stop a counter-attack.
Carlo Ancelotti continued to rotate his side, making seven changes to the team who drew 1-1 at home to Roma last weekend and fielding his 14th different line-up in as many games in charge.
Raul Albiol, Marek Hamsik, Milik and Jose Callejon were among the players rested ahead of Tuesday evening's (Wednesday morning AEDT) UEFA Champions League match at home to Paris Saint-Germain.
Napoli have 25 points from 11 games, three behind leaders Juventus who host Cagliari on Saturday evening (Sunday morning AEDT).
Watch the FIFA World Cup 2026™, Tour de France, Tour de France Femmes, Giro d’Italia, Vuelta a España, Dakar Rally, World Athletics / ISU Championships (and more) via SBS On Demand – your free live streaming and catch-up service. Read more about Sport
Have a story or comment? Contact Us

