Nash followed Ian Millward to Castleford at the end of last season after playing 30 games for Leigh in his previous spell.
The 25 year old previously played for Widnes Vikings and Salford City Reds.
Commenting on his return, Leigh Centurions boss Paul Rowley said “He’s not been getting in their first team, he knows what we are about. He doesn’t really need many introductions. There shouldn’t be too much of a transition for him and he gives us some depth and opportunities in the forward area.”