 After sidelined for three matches over injury in April, Horwood returned to the first team, where he won a penalty to allow Omar Bogle successfully convert a penalty, in a 1–1 draw against Dover Athletic on 12 April 2016.However, Horwood was not included in the matchday squad as Grimsby beat Forest Green Rovers 3–1 in the 2016 National League play-off Final at Wembley Stadium, seeing Grimsby promoted into League Two after a six-year absence from the Football League.After making the total of 12 appearances, Horwood was not retained when his loan expired at the end of the season.