The 27-year-old's future is currently the subject of much discussion, with Fulham and Tottenham Hotspur both thought to be keen to sign him during this summer's transfer window.
A recent report claimed that Man United were open to offers in the region of £30m for the Scotland international, who scored 10 goals and registered three assists in 43 appearances at club level last term.
However, Ten Hag has said that the Red Devils want to keep hold of the midfielder, calling him "a highly interesting player" for the team.
"I think we have very good players so they'll always have an interest from other clubs," the Manchester Evening News quotes Ten Hag as saying.
Ten Hag confirms Man United want to keep McTominay
""If you score 10 goals in a season and perform very well for Scotland there will be an interest. We want to actually keep him because he's a very important player for our squad.
"We've seen what he can contribute last season. When we had the sixes and he could play in a more advanced role, he's a highly interesting player for our team."
McTominay scored seven Premier League goals for the Red Devils last season, while he also netted twice in the FA Cup and once in the Champions League.
The Scot has now represented Man United on 252 occasions, scoring 29 goals and registering eight assists in the process, including 19 goals and four assists in 176 Premier League appearances.
McTominay is yet to feature for the 20-time English champions during pre-season, but he is expected to travel with the team to United States next week for their tour.
Will Casemiro leave Man United this summer?
Casemiro's future remains the subject of much speculation, with clubs from Saudi Arabia believed to be interested in signing the Brazil international this summer.
However, as it stands, it does appear that the 32-year-old will be staying, as he has another two years left on his contract, with the option of an additional year.
Casemiro has featured in both of Man United's pre-season matches, wearing the armband in the process, as he was not in the Brazil squad for the Copa America.
Unless a suitable offer arrives, which is certainly possible, the ex-Real Madrid midfielder is expected to stay with Man United beyond the end of the summer transfer window.
However, Christian Eriksen is expected to leave, while Donny van de Beek secured an exit earlier in the window, ending his time at Old Trafford by making the move to Girona.