Mulvey, 19, featured for Curzon Ashton in their youth system, scoring seven goals in as many games in their run to the third round of the FA Youth Cup in 2020/21.
He later joined Rochdale in Football League One in January 2020.
On what attracted him to the club, he said: "The facilities. The tunnel, the changing rooms and the stadium. Everything about it, it's great. It's modern, amazing and I can't wait to get started."
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