Ian Rapoport of NFL Network reported the news Tuesday, though no terms of the deal have been reported at this time.
McCarron, 28, visited the Texans on Monday after being released by the Oakland Raiders last week, according to the Houston Chronicle's Aaron Wilson. He played the 2018 campaign in Oakland after being traded by the Buffalo Bills, who originally signed him to a two-year, $10 million deal last offseason.
The Raiders traded a fifth-round pick to Buffalo for McCarron to attempt just three passes with the team.
Watson was the only Texans quarterback to throw a pass last season. Brandon Weeden served as Watson's primary backup. Weeden is currently a free agent.
McCarron spent his first four NFL seasons with the Cincinnati Bengals, where he backed up Andy Dalton. He's thrown for 928 yards six touchdowns against two interceptions while appearing in 13 games during his NFL career, including three starts during the 2015 season.
It's been a bit of a precipitous fall for McCarron, who was one of the league's most highly regarded backups in Cincinnati. After failing to impress in Buffalo and Oakland—the coaching staffs for both teams have chosen to keep Nathan Peterman over him—McCarron will have to do some image rehab in Houston if he ever wants to get a chance to compete for a job.
If not, he may be settling into career backup status.