The 34-year-old, who has fallen down the pecking order in the last two seasons, revealed he needs a new challenge away from the Chloorkop-based side.
"My contract with Sundowns expires this season, and to be fair, I have served them with flying colours and have won many things, but I'm looking for a new challenge," Modise told SunSport.
He further added that he will hang up his boots in the next two seasons to focus on his businesses.
"I will retire from football in two seasons to focus on my business. Football has taken so much of my time, but I hope I won't be lost in the game because I want to plough back to the community through the sport," Modise said.
Modise has been with Sundowns for six years, and has won two league titles, the Nedbak Cup, the Telkom Knockout Cup as well as two continental crowns - Caf Champions League and Caf Super Cup.
"I still have the passion for football and I want more game-time," Modise said.
"It's time to move on and retire somewhere in a completely new environment. Sundowns will understand as well, it's nothing personal. I'm expensive but happy to take a pay cut," Modise said.