Valentine, 25, follows team-mate Ross Killock to Bower Fold and is the sixth confirmed member of Simon Haworth's squad for 2019/20.
Ross Dent, Scott Bakkor and Greg Wilkinson have already agreed terms.
Former Republic of Ireland international defender Stephen O'Halloran is another new face at the club.
O'Halloran, 31, joins from FC United where he made 45 appearances last season, and has also played for Coventry, Stockport and Salford.
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