Bagwell retired in December as Houston's leader in homers (449), RBIs (1,529), walks (1,401) and extra-base hits (969). He finished with a .297 career average.
Along with Craig Biggio, Bagwell led the Astros to four division titles and the team's first NL pennant in 2005. He will be the eighth Houston player to have his number retired.
The Astros also honored Bagwell in a ceremony before Friday's game against St. Louis. Bagwell played his entire career with Houston and now works in the front office.
"I can't think of a better guy to be associated with over my career," said Biggio, Bagwell's teammate for 15 seasons. "He'll tell you that I made him a better player and he made me a better player."