The former presenter resigned from ITV last May after admitting to an “unwise but not illegal” affair with a younger male colleague, and has made few public appearances since.
On Wednesday, Schofield, 62, wrote on Instagram: “Now you know how I spent my Summer! Alone for 10 days, no food, no water, no crew. My story of survival, both on a desert island and off it.
“Cast Away starts Monday on @channel5_tv & My5 at 9pm.”
He also posted an image of himself on a beach with his normally clean shaven face looking shaggy with a white beard, and wearing shorts and a T-shirt.
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The three-part show, Cast Away, follows a “celebrity marooned on an uninhabited tropical island off the coast of Madagascar for 10 days”.
Before the announcement, the channel posted a short clip of a mystery star walking across a remote beach, as it teased its “brand new” desert island programme on social media.
During the first season of Cast Away, comedian Ruby Wax was left on an island in the the Indian Ocean for 10 days, and had to document her own story with body and hand-held cameras.
Channel 5 has said that Phillip Schofield being left on an island with a handful of cameras will allow him to “confront the challenges of total isolation, the forces of nature, and provides the time to battle within his own mind as he explores his own controversial story”.
The three-part series will air across three nights from Sunday until Tuesday at 9pm on each of those days.
Schofield said: “This is most definitely a first for me and the only thing I felt compelled to do. It appealed to me on so many levels.
“I’ve recently had a lot of time to think about my life, what went right and what went wrong, but I’ve always had the safe arms of friends and family wrapped around me. This time it’s just me, no ‘phone, no comforts, no crew and only lip balm as a luxury.
“I’m looking forward to exploring the island, trying to tie knots to secure my shelter and foraging and fending for myself in the wild … with no help. Maybe I’ll be Robinson Crusoe, or maybe I’ll just be Tom Hank’s Wilson and quietly drift off into the wild blue yonder.”