The 22-year-old made two senior appearances while at Craven Cottage and had loan spells at Shrewsbury and Portsmouth.
After leaving Fulham, he spent the 2015-16 season at Dagenham & Redbridge, playing 38 times in League Two.
Last season, Passley made 13 appearances in National League South for Whitehawk.
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National League side Dover Athletic have signed former Fulham defender Josh Passley on a one-year deal.