Neill, 34, joins Al Wasl after spending the 2011-2012 season with fellow UAE side Al Jazira.
"I'm delighted to be joining Al Wasl," Neill told inspiresg.com. "My family and I really enjoyed our time in the UAE last season, and having already experienced the Pro League I'm looking forward to another challenging season here.
"I'm also looking forward to working with Bruno Metsu, who is one of the most experienced and respected coaches in this region, and I'm hopeful of being able to help the club achieve its ambitions."
Neill has previously had spells in England with Millwall, Blackburn Rovers, West Ham United and Everton, before a stint in Turkey with Galatasaray.