It's the second win in a row for Toronto as the Marlies improved to 6-0-1 on the season, the best start in franchise history.
David Ling scored two goals, while Darryl Boyce and Kris Newbury, with an empty-netter, had singles for the Marlies in front of 3,274 fans at Ricoh Coliseum.
Mitchell also had two assists for a three-point game, while Newbury had one helper for a two-point night.
Zenon Konopka and Philippe Dupuis replied for the Crunch.
Syracuse, which has lost four of its past five games, fell to 3-7-0. Toronto and the Chicago Wolves, also 6-0-1, are the only AHL teams that still haven't lost a game in regulation time this season.
Marlies netminder Justin Pogge stopped 32 of 34 shots for the victory. At the other end, Crunch goalie Adam Munro made 21 saves on 26 shots.
Toronto and Syracuse both went 1-for-6 on the power play.
The game was tied 0-0 after the first period and 1-1 through 40 minutes.
Boyce opened the scoring for Toronto at the six-minute mark of the second period when he swatted in a rebound from the side of the net past Munro. The Crunch made it 1-1 on Konopka's power-play goal at 7:46 of the middle frame, as the Syracuse centre positioned himself at the foot of the Marlies crease and redirected a pass past Pogge.
Ling regained the lead for Toronto early in the third period, standing at the side of the net and tapping in Mitchell's pass at 2:23. A few minutes later, Dupuis pulled the Crunch even at 2-2 when the puck bounced to him during a goalmouth scramble and he fired a shot past Pogge at 7:01. Ling provided insurance at 17:53 when he snapped a wrist shot past Munro, while Newbury's empty-net goal sealed the game at 18:48.
The Marlies, who played six of their first seven contests at home, kick off a seven-game road trip in Albany River against the Rats on Wednesday.