The winger was released by then Coventry City manager Chris Coleman back at the end of March but after recovering from injury, Cain has impressed during pre-season including last Saturday's game against Tranmere when he was a 54th minute substitute.
The first ever winner of the Covsupport News Service Coventry City U18's Player Of The Year in 2009, Nuneaton born Cain has signed a one year deal and teams up with former City youth and reserve team keeper Neil Collett.
Speaking to his club's website, Mansfield boss David Holdsworth said: "Ashley is an exciting prospect. He has created a good impression and I hope he has a good season with us."
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