Theodore signed with the team in July after spending last season with Minnesota.
He was part of an overhaul that followed a 30-40-12 season and last-place finish in the Eastern Conference. The Panthers fired head coach Peter DeBoer after the season and named Kevin Dineen their new leader in June.
Dineen made his head coaching debut Saturday and got a victory thanks to Theodore, who faced 22 shots over the final two periods but stopped them all. Stephen Weiss and Jason Garrison scored first-period goals in the victory.