The Scotland international was back with the squad on Monday morning after missing Saturday's 1-0 defeat to Torino with an ankle injury.
According to Il Mattino, McTominay trained without restrictions and is expected to be available for selection when Napoli face PSV on Tuesday in their third Group Stage fixture.
McTominay had required three stitches following a training-ground knock last week and was left out of the travelling party to Turin as a precaution.
His return offers a welcome boost for coach Antonio Conte, who is looking to get Napoli back on track after a mixed start to their European campaign.
Hojlund, however, remains unavailable. The Danish forward, who also missed the defeat to Torino, is still recovering from muscle fatigue and has not been deemed fit to travel.
The former Manchester United striker's absence continues to limit Napoli's attacking options, with Giovanni Simeone likely to start again up front.
Napoli have collected three points from their opening two Champions League matches, leaving them eager to build momentum in Eindhoven.
After the European tie, they will quickly turn their attention back to Serie A, where they are set to host title rivals Inter Milan on Saturday, a fixture that could have early implications in the Scudetto race.
Conte will hope McTominay's return adds stability and drive in midfield as Napoli aim to bounce back both in Europe and domestically.
Enzo Maresca has admitted Chelsea are still unsure when Romeo Lavia will return, as the Belgian's injury problems continued to disrupt their midfield plans ahead of Saturday's trip to Bournemouth.
Aleix Garcia is enjoying the best spell of his career, turning himself into a key figure in Bayer Leverkusen's midfield and pushing for a place in Spain's 2026 World Cup squad.
Roberto De Zerbi has made it clear he plans to stay at Marseille and aims to turn the club into a contender for major trophies as they push through a crucial phase of the 2025 season.
Napoli scraped into the quarterfinals of the Coppa Italia on Wednesday after surviving a nail-biting 9-8 penalty shoot-out win over Cagliari, following a 1-1 draw in regulation time at the Stadio Diego Armando Maradona.
