The 29-year-old Scotland international underwent a planned ablation procedure at Manchester's Spire Hospital in September after being diagnosed with a mild, benign arrhythmia.
McTominay has since undergone further tests and been cleared to resume sporting activity. He has returned to training with Napoli and will be available for selection by coach Massimiliano Allegri.
"Scott McTominay underwent further diagnostic tests, which showed that he is fit to play. The Napoli player therefore resumed training with the rest of the team after the period spent training separately," the club said in a statement.
McTominay has not played since August 30 and missed Napoli's 3-2 Serie A defeat by champions Inter Milan as well as their Champions League loss to Arsenal.
Napoli, who are ninth in the Serie A standings, host sixth-placed Frosinone on Saturday.