[1] Born in Baulkham Hills, New South Wales,[1][2] Gannon is one of the Ipswich Grammar School Old Boys.
[1] Gannon made his first-class debut in a Sheffield Shield match against Tasmania in October 2010.
Gannon signed with the Brisbane Heat in 2012 and made his Twenty20 debut in the 2012–13 Big Bash League season.
In August 2019, he was named in the United States' squad for the Regional Finals of the 2018–19 ICC T20 World Cup Americas Qualifier tournament.
[9] In January 2021, USA Cricket named Gannon in a 44-man squad to begin training in Texas ahead of the 2021 Oman Tri-Nation Series.