14th August 2018, 08:04 | Leeds
The 18-year-old half-back, who is a product of Castleford Tigers' academy, joined rugby union side Edinburgh last November and was contracted to the Scottish Rugby Union.
However, the Rhinos have agreed an undisclosed fee with the SRU to sign McLelland on a three-and-half-year deal and he has already begun training with them.
McLelland played rugby league for England at under-16 and under-18 level but has a grandfather from East Ayrshire and won eight caps for Scotland under-20s.
McLelland said: “I have enjoyed my opportunity in rugby union and would like to thank Richard Cockerill, all the coaches and players at Edinburgh and with Scotland under-20 who worked with me over the past year.
“The chance to come home to West Yorkshire and be part of something special here at the Rhinos was something that was very attractive to me.
“When you look around the stadium and speak to Kevin Sinfield about the plans for the team moving forward, I knew it was the right move for me.”
McLelland has joined Leeds too late to play for them this year but the club say he will be part of their first-team squad for 2019, when he will also still be eligible for the under-19s.
Leeds director of rugby Kevin Sinfield said: “Callum was a huge loss to our sport when he left and it is great to welcome him back.
“He is an outstanding talent and, in his age group, he is up there with the very best.
“There were a host of clubs who were chasing his signature and it is brilliant news for Leeds Rhinos that he has agreed to join us.”