Aberdeen players Scott McKenna, Kenny McLean and Ryan Christie have been named in new manager Alex McLeish's Scotland squad for the worldwide friendlies against Costa Rica and Hungary later this month.
The 21-year-old, who has played in United's last seven matches across all competitions, could find himself having to step up even more for the Manchester United first-team before the end of the season if the club's injury concerns don't ease up.
Lancaster-born McTominay has previously stated he sees his worldwide future with the country of his father and reportedly pledged to represent Scotland this month following a meeting Alex McLeish.
Oli McBurnie and Barry Douglas will earn their first Scotland call-ups when Alex McLeish names his squad later on Monday.
McLeish spoke to Mourinho about McTominay's global future but the United boss allowed the player to make his own decision.
Jose Mourinho has handed the 21-year-old starts in crucial games against Sevilla, Chelsea and Liverpool in recent weeks and McTominay has helped United secure positive results each time.
Barnsley striker Oli McBurnie, Wolves left-back Barry Douglas, Hearts goalkeeper Jon McLaughlin, Hibernian midfielder Dylan McGeouch and Aberdeen defender Scott McKenna are all also included in the Scotland squad.
Scotland face Costa Rica on March 23 at Hampden Park before travelling to Budapest to take on Hungary four days later.