Gimenez, 27, hit a groundball base hit into right-center to bring home Kazuma Okamoto from third, finishing the game responsible for all three of the Blue Jays' runs.
After going down 1-0 from a Shea Langeliers solo home run, Gimenez hit a bases-clearing triple in the bottom of the fifth to put the Jays up 2-1.
Langeliers would hit another home run to tie it all up 2-2 in the top of the ninth before Gimenez walked it off just shortly after.
Gimenez and Okamoto, who made his MLB debut after being signed off the international free agent market from Japan, both finished the game going 2-for-3 at the plate.
Starting pitcher Kevin Gausman also had a historic outing, putting up an Opening Day franchise record with 11 strikeouts (more here).
The Blue Jays are coming off a World Series loss to the Los Angeles Dodgers that went the full seven games. They earned their first AL East title since 2015.
Game two of the opening series against the Athletics will take place on Saturday, March 28th.