Fighting Saturday night at the Air Canada Centre, Gagnon connected with a devastating left hand and later submitted Walel (The Gazelle) Watson with a rear naked choke just 69 seconds into their bantamweight bout at UFC 152, according to TSN.ca.
Gagnon, 5-6 and 135-pounds, improved to 9-2 while Watson, who fights out of San Diego, fell to 9-5.
The 27-year-old's first fight was at UFC 149 against Bryan Caraway. Gagnon lost by submission in the third round to Caraway in his UFC debut last July in Calgary. It was deemed Fight of the Night and both fighters earned $65,000 for their efforts.