Mills completed seven of 12 passes for 79 yards in Sunday's 34-7 loss to the Vikings in Week 3.
Mills and the Texans agreed Wednesday on a one-year, $5 million extension, Ian Rapoport of NFL Network reports.
Mills is dealing with an injury to his ribs and may not play in Saturday's preseason game against the Giants, Aaron Wilson of SportsTalk 790 reports.
Mills completed 8-of-13 attempts for 89 yards and was sacked twice in Friday's 20-12 preseason win over Pittsburgh.
Mills has one year remaining on his rookie contract entering the 2024 offseason. He completed 18 of 39 passes for 173 yards and two touchdowns in 2023.
Mills completed 15 of 32 passes for 149 yards and two touchdowns in Sunday's 36-22 loss to the Browns. He also completed a two-point conversion.
Mills was sacked for a 10-yard loss on his only play of Sunday's 19-16 overtime win over the Titans in Week 15.
Mills is slated to remain the Texans' No. 2 quarterback Sunday against the Titans while Case Keenum draws the start in place of C.J. Stroud (concussion), who has been ruled out for the Week 15 contest, DJ Bien-Aime of ESPN.com reports.
Mills is expected to remain the Texans' No. 2 quarterback for Sunday's game againt the Titans with Case Keenum in line to draw the Week 15 start in place of C.J. Stroud (concussion), Aaron Wilson of KPRC 2 Houston reports.
Mills completed one of five passes for four yards after replacing C.J. Stroud (concussion) in the fourth quarter of Sunday's 30-6 loss to the Jets.