Commissioner Jay Monahan announced the change to tour members on Monday.
The term runs through the end of 2024. Spieth's selection was voted on by the five other player directors: Tiger Woods, Patrick Cantlay, Charley Hoffman, Peter Malnati and Webb Simpson.
"With Rory McIlroy resigning from the PGA Tour Policy Board last week, per the PGA Tour Tournament Regulations, the five remaining Player Directors have elected Jordan Spieth to serve the remainder of Rory's term which expires at the end of 2024," Monahan wrote to members, according to an email obtained by Golf Channel.
"Jordan has extensive experience with the Tour's governance process, having served two years on the Player Advisory Council (2017-18) including PAC Chairman in 2018 and three years (2019-21) as a Player Director."
McIlroy resigned last week, citing the time commitment as the biggest factor. He also acknowledged that the agreement between the PGA Tour and DP World Tour with Saudi Arabia's Public Investment Fund (PIF), which backs LIV Golf, over future cooperation affected his role on the board.
Spieth is a 13-time winner on the PGA Tour with major victories at the Masters (2015), U.S. Open (2015) and The Open Championship (2017).
