Pavel Gogolev and Danny Zhilkin scored in the tiebreaker for Guelph, which has picked up points in six straight games.
The Storm are four points clear of the Owen Sound Attack and sit in sixth place in the Ontario Hockey League’s Western Conference.
Rory Kerins scored the lone shootout goal for the Greyhounds, who are four points out of a playoff spot with the loss.
Clark Hiebert and Eric Uba scored in regulation for the Storm, while Joe Carroll and Tye Kartye provided goals for the Soo.
Bailey Brkin stopped 29 shots in the loss.
It was the second straight game for the Storm that went to a shootout, after their loss the Flint Firebirds 4-3 on Saturday.
The Storm return to action on Friday when the London Knights come to town. Larry Mellott will have the call from the Sleeman Centre live on 1460 CJOY at 7:30 p.m.
BELOW: Highlights of the Flint Firebirds’ 4-3 shootout win over the Guelph Storm on Saturday.