Mitchell was selected by the Hawks with Pick No.29 in the 2020 NAB AFL Draft and has been on the Hawks' rookie list since.
The 20-year-old has been averaging 22 possessions and 6.5 marks per game.
"It's a real thrill that Seamus has been named to play his first game, he absolutely deserves this opportunity," McCartney told hawthornfc.com.au.
"Gifted with genuine speed, Seamus has shown a great ability to play a rebounding defender role and be a real weapon for his side in generating offensive drive."
"Seamus has shown great resilience during his short time here at the club, battling through multiple injuries to return to the field and play the sort of football we all knew he could."
"I'm sure plenty of Seamus' family and friends will be jumping in the car to make the trip to see his first game in Gather Round."
Hawthorn will take on the Giants at Norwood Oval on Sunday at 3:20 pm (AEST).