The defenseman, who was acquired by the Blues in a trade with the Montreal Canadiens on July 1, had one assist in 19 games entering Friday.
Matt Luff also scored his first goal with the Blues, and Robert Thomas had two assists for St. Louis (12-14-7), which had lost two straight, including 7-2 at the Nashville Predators on Thursday. Joel Hofer made 27 saves.
Andre Burakovsky had a goal and an assist, and Connor Bedard had two assists for Chicago (13-12-6), which has lost three of four. Spencer Knight made 23 saves.
Mailloux made it 1-0 at 3:41 of the first period during a delayed penalty. Thomas feathered a pass across the ice for Mailloux, who then stepped into the left face-off circle and beat Knight with a wrist shot to the far side.
Luff pushed the lead to 2-0 at 11:48, taking a pass down the slot from Robby Fabbri and scoring to the glove side. It was his first goal since April 4, 2023, when he scored for the Detroit Red Wings against the Canadiens.
Wyatt Kaiser cut the deficit to 2-1 at 15:50. He took a pass from Burakovsky, skated to the high slot and beating Hofer high to the left side.
Faulk restored the two-goal lead at 3-1 at 8:57 of the second period. After receiving a pass from Tyler Tucker at the bottom of the right circle, he moved in and stuffed a shot under Knight’s arm at the near post.
Burakovsky made it 3-2 at 14:08 of the third period. After Bedard deflected Colton Parayko’s poke of the puck deep in the St. Louis zone, it squirted across the top of the crease to the right post, where Burakovsky scored with a backhand.