The street race near Exhibition Place will be held June 14 — over a month earlier than its usual time — so it doesn't conflict with the July 10-26 Pan Am Games.
"Today's a good day to wave both the green and checkered flags," Honda Indy Toronto president Charlie Johnstone said in a release. "Scheduling an event of this magnitude is complicated in a normal year. Toronto is a growing city with many moving parts, and the same can be said for professional auto racing.
"There are a lot of details and co-ordination that go into the teams, the schedules, the races and the various sites, especially with street courses. We're celebrating today and getting ready for the road ahead."
The event used a doubleheader format last summer.
The first race was scheduled for July 19 but was postponed a day due to heavy rain. Sebastien Bourdais won the opener on the morning of July 20 and Mike Conway took the second race later that day.
IndyCar unveiled its full 2015 schedule Thursday. The 17-race calendar kicks off March 8 in Brasilia, Brazil and wraps up Aug. 30 at Sonoma Raceway.