The Texans added Fiedorowicz, 26, to the reserve/retired list on Wednesday.
"We have a lot of respect for C.J. and we support his decision to retire," Texans coach Bill O'Brien said in a statement. "I know this was a difficult decision for him. C.J. has been a great teammate and we appreciate his efforts over the past four years. We wish him success in the next phase of his life."
Last August, the Texans signed Fiedorowicz to a three-year, $22 million contract that included $10 million guaranteed. According to the Houston Chronicle, the Texans reworked Fiedorowicz's contract when he retired.
When the Texans signed Fiedorowicz to the extension, they included a de-escalator that would reduce his base salary by $2.8 million if he were to be cut or retire due to a preexisting condition such as a concussion.
Fiedorowicz suffered his first concussion of 2017 in training camp and his second in the Texans' season opener. He was placed on injured reserve in early September but returned to the active roster in Week 10. Three weeks later, Fiedorowicz left a game against the Tennessee Titans with a concussion and was placed on IR again.
While Fiedorowicz was on injured reserve at the beginning of last season, the Texans primarily relied on tight ends Ryan Griffin and Stephen Anderson. Griffin also suffered two concussions last season and was placed on IR in November.