His first post in management was at Halifax Town, initially as coach to Alan Ball Senior and then in 1970 as first team manager. He spent only one full season in charge, giving the club their most successful ever campaign just missing out on promotion to the old second division. He started the 1971–72 season by leading Halifax to a 2–1 Watney Cup victory over a full strength Manchester United side, which included George Best, Denis Law and Bobby Charlton. Just a week later Kirby left Halifax to take charge at Watford where he remained until May 1973. At Watford, injuries, boardroom unrest, and a shortage of luck and money, conspired to produce two terrible winters consisting of one humiliation and very nearly a second.
In 1978 he left Akranes and returned to Halifax. Kirby inspired the team to another famous victory over Mancunian rivals; this time it was the turn of Malcolm Allison's Manchester City, who fell to a single Paul Hendrie goal in an FA Cup 3rd round tie in January 1980. His second spell with the Yorkshire club ended in June 1981 after a string of poor results saw his team finish second bottom of the old 4th division.