 Mellis made his Oldham Athletic debut, coming on as a substitute for Carl Winchester in the 72nd minutes, in a 3–2 loss against Gillingham two days later.After spending two months without being used in the first team, Mellis made his Oldham Athletic return, where he came on as a substitute for Joseph Mills in the 77th minutes, in a 2–0 loss against Crawley Town on 6 April 2015.Mellis went on to make seven appearance for the club.