Galloway started 14 games at left tackle over the last two seasons.
"I'm done with football," Galloway wrote in a text to Robert Allen of Sports Illustrated's Pokes Report on Wednesday. "I was getting hurt so much and I felt like all of my injuries were piling up to where they were effecting me too much on and off the field."
Sources confirmed to ESPN's Mark Schlabach that Galloway has officially retired.
The 6-foot-5, 270-pounder missed four games last season due to an ankle injury, and he's also struggled with shoulder issues in each of the past two years.
Galloway was supposed to be one of three returning offensive linemen for the Cowboys, whose offense is centered around star running back Chuba Hubbard. Hubbard led the FBS with 2,094 rushing yards in 2019.