Alexander signed with the
Montreal Alouettes on February 7, 2022. During the final preseason game against the
Ottawa Redblacks, he drove the team 71 yards for a 27–26 win. Following training camp, he began the season on the practice roster, but was elevated to the active roster on June 23, 2022, against the
Saskatchewan Roughriders, where he dressed in his first professional game. He reverted to the practice roster after
Vernon Adams was moved back to the active roster in a backup capacity. In that game, Alexander completed eight of 13 pass attempts for 89 yards and an interception. After Evans led the Alouettes to 74 yards of net offence and three points in the first half, Alexander started the second half in his first meaningful playing time in the CFL. Alexander then started the
Thanksgiving Day Classic against the
Ottawa Redblacks and won his fourth start of the season. On November 26, 2024, it was reported that Alexander had signed a three-year contract extension with the Alouettes, indicating a commitment by the team to make him the starting quarterback for
2025. This was confirmed when the Alouettes traded Fajardo to the
Edmonton Elks during the offseason. He began the 2025 season as the opening day starter and led the Alouettes to three straight wins before suffering a hamstring injury. He missed the following two games, both losses, and returned following a
bye week on July 17, 2025, against the
Toronto Argonauts. He completed 26 of 39 pass attempts for 303 yards with one touchdown pass and one interception, but re-aggravated his hamstring injury on a touchdown run in the Alouettes win. Davis won his next two starts, extending his record to 11 consecutive wins, before resting in the final game of the regular season with Montreal's playoff position already secured. He finished the regular season having started in seven games, recording 158 completions our of 218 attempts for 2,024 yards with ten touchdown passes and three interceptions. After getting the ball back with the score tied 16–16 with 1:41 left in the fourth quarter, Alexander led the Alouettes on a seven-play, 37-yard drive to set up
José Carlos Maltos's game-winning 45-yard field goal. ==CFL career statistics==