Mullins joined League Two club Kidderminster Harriers on loan for the remainder of 2004–05 on 17 December 2004, making his debut one day later in a 2–0 defeat away to Cheltenham Town. He scored his first goal for the club on 29 January 2005 in a 3–1 win away to Cambridge United. Mullins also scored the only goal of the reverse fixture against Cheltenham Town on 5 March. His season was ended by a hamstring injury in a 1–1 draw with Yeovil Town on 16 April, having made 21 appearances for the club.