In a statement released by the Chiefs, Polwart says he is grateful for the opportunities rugby has provided and the support he has received.
"It has been a difficult decision to make to leave the game I love. It has provided me with plenty of great friendships and some awesome experiences. I have had some ongoing issues with concussion, and while I am currently symptom-free, I chosen to hang up my boots and not to put myself at further risk."
Polwart made his debut for the Chiefs back in 2017, and amassed 26 Super Rugby caps as well as 15 NPC games for Bay of Plenty.
Chiefs forwards coach Neil Barnes was complimentary of Polwart's courageous decision, saying he is a fantastic individual.
"It is a testament to his character to have chosen to make this decision for his own well-being and we applaud him for being so courageous. We wish him all the best for the future and hope he will return to the game and inspire a future generation.