The former Manchester United star has now banged in four goals this season, with three coming in the Italian top-flight.
After scoring the winner over Torino in the top-flight, McTominay ran straight to boss Antonio Conte to celebrate.
McTominay's goal came just past the half-hour mark, with the Scot breaking the deadlock from Khvicha Kvaratskhelia's pulled back pass to fire a left-footed shot into the net.
Conte is enjoying a brilliant start to the season since taking charge of Napoli in June - his first managerial role since leaving Tottenham in March 2023.
Before leaving Spurs, he hit out at the club's history following a draw away at Southampton, where he memorably said: "Tottenham's story is this.
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"Twenty years there is the owner and they never won something, but why? The fault is only for the club, or for every manager that stays here?"
Despite failing to win silverware in north London, Conte could end his debut season in Naples with a Scudetto title.
Napoli have won ten games in the campaign so far, drawing and losing two apiece.
And McTominay has played a vital role in the club's strong start following his £25million move from Old Trafford in the summer.
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His debut goal came in a 5-0 win over Palermo in the Coppa Italia on September 26, and a week later he scored for the first time in Serie A.
He found the back of the net in just 25 seconds to kick start a 3-1 victory over Como.
McTominay has also assisted twice in the top-flight and appears to be enjoying life in Europe, playing alongside former Premier League rival Romelu Lukaku.
Lukaku, who joined Napoli on a permanent deal from Chelsea, has scored five times and assisted four in 12 Serie A games so far this season.
And Napoli also have Billy Gilmour on their books having forked out an initial £12m on him from Brighton.
After a slow start to life in Italy, he has now made ten appearances so far for Napoli in all competitions.
Next up for Napoli is a double-header with Lazio, where they face the Rome outfit on Thursday in the Coppa Italia, before welcoming them to the Stadio Diego Armando Maradona three days later.