Horton became player-manager of Hull City in July 1984, and led his side to promotion to the Second Division at the end of the 1984–85 season. He quickly built up a reputation as a "strong-minded, tactically-aware coach." Due to the League Cup draw, three of his first four games as manager were against Lincoln City, and his very first game in charge was a 0–0 draw at Sincil Bank. In November, his team came from 4–1 down to beat Leyton Orient 5–4 after he instructed assistant manager Chris Chilton to "get some verbals going" at half-time. He signed former Luton Town teammate Frankie Bunn as a replacement for top-scorer Billy Whitehurst, who he sold to Newcastle United for £232,000. After promotion was secured, Horton was offered a place on the board of directors.