Mellor had been involved in the Bradford Bulls scholarship system from under-15's.
In the 2013 season, he featured in Round 20 Warrington and Round 27 against Huddersfield.
In the 2014 season, Mellor featured in the pre-season game against Hull FC. He featured in Round 10 Wigan to Round 13 Huddersfield then in Round 21 against Huddersfield to Round 23 Leeds. He played in Round 27 London Broncos. He signed a new one-year deal with the Bradford outfit despite their relegation to the Championship.
In the 2016 season, Mellor featured in the pre-season friendlies against Leeds and Castleford. He featured in Round 2 (Whitehaven) to Round 3 Swinton Lions then in Round 5 Oldham to Round 7 London Broncos. He played in Round 10 (Dewsbury Rams) to Round 13 against Swinton then in Round 15 against Leigh. Mellor featured in Round 17 (Workington Town) to Round 21 Whitehaven then in Round 23 Featherstone Rovers. Mellor featured in the Championship Shield Game 1 Whitehaven to the Final against Sheffield. Mellor played in the Challenge Cup in the 4th Round against the Dewsbury club.
Huddersfield Giants
Following Bradford's liquidation before the 2017 season, he signed a three-year deal with Super League side Huddersfield.[4]
Mellor featured in Round 1 against Widnes to Round 6 against Wigan.
On 21 June 2022, the Castleford Tigers announced that Mellor would join the club with immediate effect, having signed a two-and-a-half-year deal.[6] He made his Tigers debut later that week, in a golden-point win against the Catalans Dragons at Wheldon Road.[7][8] He scored his first try for the club against his former side Huddersfield on 19 August.[9]
Ahead of the 2023 season, Mellor was assigned squad number 12 and also appointed Castleford vice-captain.[10][11] On 12 May, playing as a centre, he scored two tries for Castleford in their 22-46 loss against the Catalans Dragons.[12] Three weeks later, at the 2023 Magic Weekend, he scored two tries in Castleford's 26-24 win against Leeds.[13] Mellor made 25 appearances throughout the season as the club narrowly avoided relegation by finishing above Wakefield.[14] He said, "We've massively underperformed as a team," and that looking forward, "There's a lot of improvements that need to happen across the board."[14]
Mellor suffered a knee injury in a friendly against Keighley ahead of the 2024 season, forcing him to miss the opening two rounds.[15] He displayed impressive form as the season progressed with Castleford director of rugby Danny Wilson praising his "tough line-running",[16] and subsequently signed a two-year contract extension in May.[17] On 12 July, Mellor scored two tries in the Tigers' round 17 win against London.[18]
Club statistics
Appearances and points in all competitions by year