Gately, who died in 2009, had recorded a demo version of I Can Dream for his solo album back in 2002; and now his bandmates have added their voices.
In a statement, Ronan Keating, Keith Duffy, Mikey Graham and Shane Lynch said: “When we started out as five young Dublin Northsiders, eager to face the world, we never imagined that we’d still have an army of fans some twenty-five years later.
“If you’d seen our famous first TV appearance on The Late Late Show, you’d probably be surprised too!
“We really can’t put into words just how much the fans, have supported us along the way. Without that support, we would have never achieved what we have, and for that we’re eternally grateful.”
They added: ”Twenty-five years is a long time. We’re certainly not boys anymore, and we all feel that we should now call time on our lives together as Boyzone and go out on a real high.”
The group will release their final album Thank You And Goodnight on November 16, featuring material co-written by the likes of Ed Sheeran and Gary Barlow.
Of I Can Dream, they said: “The loss of Stephen left scars that we will carry as a band forever.
“We were immensely touched by all the tributes and messages of support that helped us through the dark days. Stephen was our brother and will always be at the very the heart of Boyzone.
“It was a bittersweet experience to hear all our voices together again. It’s the closest the five of us will ever get to being in a room together again making music.”
They will tour in 2019, with tickets on sale from 9am next Friday, June 22.
Scroll down for the list of dates.
Sat 26 Jan – SSE Hydro Arena, Glasgow
Sun 27 Jan – Echo Arena, Liverpool
Tue 29 Jan – Motorpoint Arena, Nottingham
Wed 30 Jan – Metro Radio Arena, Newcastle
Fri 1 Feb – First Direct Arena, Leeds
Sat 2 Feb – Manchester Arena
Mon 4 Feb – Motorpoint Arena, Cardiff
Tue 5 Feb – Brighton Centre
Thu 7 Feb – O2 Arena, London
Fri 8 Feb – Genting Arena, Birmingham
Sat 9 Feb – Bournemouth International Centre