Pearce was a guest commentator on the Boston-area radio station, which was rebroadcasting Game 1 of the 2018 World Series.
Before his latest announcement, Pearce told WEEI in December that he was "unofficially retired."
"You know what? It has been a good run. I have 10 years in there," Pearce said Monday night. "Right now, I am officially retired."
Pearce, who turned 37 on Monday, played for seven teams in his MLB career. He finished with a .254 batting average, 91 home runs and 303 RBIs in 766 career games.
The Pittsburgh Pirates selected Pearce in the eighth round of the 2005 MLB Draft. He made his major league debut with the club in 2007 and played in parts of five seasons with the Pirates.
His best season was in 2014, when he set career highs in games played (102), home runs (21) and RBIs (49) with the Orioles.