A former teammate of manager Adam Hinshelwood at Brighton & Hove Albion, Cox joined the club 12 months ago after leaving Eastbourne Borough.
He made his debut for the club on the opening day of the season, starting the 3-1 defeat to Folkestone Invicta.
His first goal came in September when he got the ball rolling with the opening goal in the 4-0 win at Leatherhead.
The former Leyton Orient man played his part in helping the Reds secure promotion to the National League last season making 27 appearance and scoring twice.
Dean leaves with the club’s very best wishes.