Luck will have a press conference on Sunday to make it official.
"For the last four years or so, I've been in this cycle of injury, pain, rehab, injury, pain, rehab", Luck said.
Luck has played for Colts since 2012 - the year he was named the No 1 overall pick in the NFL Draft.
He finally recovered a year ago, and returned to form after one month of play, eventually leading the Colts to the AFC playoffs as a wild card by winning nine of their last 10 games.
In all likelihood, the Steelers have one less AFC North team to worry about this season, as the Colts prepare for life without Andrew Luck.
"I feel exhausted, and not just in the physical sense", he said. He missed the entire 2017 campaign while recovering from shoulder surgery.
His rehabilitation from the injury forced him to miss the entire 2017 season but he put in a stellar performance when he returned past year.
The sports world has been rocked tonight by the news that Indianapolis Colts star quarterback Andrew Luck is retiring at age 29. Kaepernick has not played an National Football League game since 2016.
"It was a good day for him and we just want to continue for him to get that confidence, keep going more and more, show that we trust in him and keep rolling", coach Matt Nagy said. "Being in that room with him for the last 18 months was just the experience of a lifetime. one of the truly unique players to ever put on an National Football League uniform and certainly to wear that horseshoe proud". In six seasons in Indianapolis, Luck threw for 23,671 yards, 171 touchdowns while leading 20 game-winning drives and starting eight playoff games.
Coach Frank Reich had said he hoped to have an answer about Luck's availability for the September 8 season opener after the third preseason game.
With Luck dealing with a variety of injuries in 2017, Brissett started 15 games for Indy, throwing for 3,098 yards, with 13 touchdowns and seven interceptions.