Heimgartner, who races a Nissan Altima for Kelly Racing in Supercars, will also form part of the team's four-car TCR Australia line-up in one of two Subarus.
He completes a KR driver roster that includes factory Subaru rally driver Molly Taylor in the other WRX, and Alex Rullo and Chelsea Angelo in a pair of Opel Astras.
The Kiwi is the first Supercars full-timer to sign on for TCR Australia, other drivers with active Supercars programmes like Tony D'Alberto, James Moffat, Will Brown and Dylan O'Keeffe either on enduro-only deals or racing in the second-tier Super2 series.
Heimgartner will test the WRX at Winton on Wednesday, before the first-ever TCR Australia round kicks off at Sydney Motorsport Park on Friday.
“I’m really looking forward to getting into the new TCR Australia Series,” said Heimgartner.
“It’s an interesting new category and to be given the opportunity by Kelly Racing, who I already have a great relationship with, is really exciting.
“All of the cars are front-wheel-drive which is something new to me. I’ve only ever raced in rear-wheel-drive categories so I’m looking forward to taking on the new challenge and getting to grips with a new type of race car.
“There are a lot of really high-level drivers in the category and some of them I’ve raced with before so I’m keen to get out there and start racing alongside them in Sydney this weekend.”
Chaz Mostert is understood to have also tried to dovetail a full-time Supercars programme with TCR Australia, but the move was blocked by Tickford Racing.
Motorsport.TV will be live streaming every race of the 2019 TCR Australia season.
Confirmed TCR Australia drivers:
Tony D'Alberto (Wall Racing Honda)
John Martin (Wall Racing Honda)
Nathan Morcom (HMO Customer Racing Hyundai)
Will Brown (HMO Customer Racing Hyundai)
Alexandra Whitley (Alliance Autosport Volkswagen)
Jimmy Vernon (Garry Rogers Motorsport Alfa Romeo)
Dylan O'Keeffe (Garry Rogers Motorsport/Ashley Seward Motorsport Alfa Romeo)
Chris Pither (Garry Rogers Motorsport Renault
James Moffat (Garry Rogers Motorsport Renault)
Rik Breukers (Melbourne Performance Centre Audi)
Molly Taylor (Kelly Racing Subaru)
Andre Heimgartner (Kelly Racing Subaru)
Alex Rullo (Kelly Racing Opel)
Chelsea Angelo (Kelly Racing Opel)