After going undrafted in the 2016 NFL draft Shiltz began working for Ernst & Young in Indianapolis at which time he was invited to the Montreal Alouettes' April mini-camp for the 2017 season.

[6] Shiltz was named the starting quarterback for the Alouettes in their Week 16 match against the BC Lions after Vernon Adams was suspended for one game.

[9] Late in the team's Week 10 match against the Redblacks starting quarterback Vernon Adams Jr suffered a shoulder injury, thrusting Shiltz into the starting role where he completed all three of his pass attempts for 36 yards setting up the game winning touchdown.

[10] The following week Shiltz started in place of Vernon Adams, and played well leading the Alouettes to a 27-16 win over the Ottawa Redblacks.

[11] The next day on October 17, 2021, the Alouettes announced that they had traded for veteran quarterback Trevor Harris, giving Shiltz competition for the position while he remained the team's starter for the next game.

[13] Shiltz ended up being benched for Harris during the following game, and was placed on the injured list, missing the rest of the season.

Shiltz began the 2023 season as the backup quarterback to Bo Levi Mitchell whom the club acquired in the off-season.

[22][23][24] After sitting for six games, he returned to the active roster, but rookie Taylor Powell continued to start at quarterback for the Tiger-Cats while Shiltz remained the backup.

[22] In total, Schiltz played in 11 regular season games, starting in three, where he completed 108 of 161 pass attempts for 1,556 yards, seven touchdowns, and five interceptions.