Kinsella admitted an FA charge after a sample he gave in February contained the anabolic steroid Nandrolone.
The 21-year-old midfielder has been hit with a 24-month suspension, backdated to the date the sample was collected, and will be banned from football until February 2015.
An FA statement read: "Following an Independent Regulatory Commission hearing, Fleetwood Town's Gerard Kinsella has been suspended from football and all football activities for two years, subject to any appeal, after he admitted an FA charge in relation to a breach of its anti-doping regulations.
"Kinsella was charged under FA Rule E25 for a breach of Regulation Three after he gave a sample following an out-of-competition test which contained the presence of a prohibited substance, namely Nandrolone, listed as an anabolic androgenic steroid in the 2013 Prohibited List of the World Anti-Doping Code.
"The player, who requested a personal hearing, will serve a 24-month suspension commencing 5 February 2013 (backdated to the date of sample collection) until 4 February 2015 [inclusive]."
Kinsella, who was on Everton's books as a youngster, signed for Fleetwood last summer but has yet to make a first-team appearance.
He did have a spell on loan with non-league Telford last season, playing seven games and scoring one goal.
A Fleetwood spokesman told Press Association Sport: "Fleetwood Town will make a full statement about Gerard Kinsella in the fullness of time.
"The verdict has only recently been made public by the FA and we have no further comment at this stage."