The pop star and actor was holidaying in Majorca when he died suddenly, the News of the World reported.
The paper said the cause of his death was unclear but a close friend said he died after a night out on the Spanish holiday island.
Boyzone's official website said Gately died "tragically" while on holiday with his partner, Andrew Cowles.
It said the rest of the band are flying out to Majorca.
Band member Shane Lynch told the News of the World: "Me and the boys are flying out in the morning.
"We just need to get over to where he's passed and work out what we need to do."
Boyzone manager Louis Walsh told the newspaper: "We're all absolutely devastated."
He said: "I'm in complete shock. I was only with him on Monday at an awards ceremony. We don't know much about what's happened yet.
"I only heard after The X Factor and we will rally around each other this week. He was a great man."
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