Beestin, 22, re-joined Tadcaster in September 2019 and began his career with the club in their development team before making a move to Doncaster.
He will feature in Scunthorpe's under 23s side.
"Since his return he has been ever present in the Tadcaster team," the club said.
"His reading of the game and ability to set things in motion from midfield has been invaluable and he leaves us with memories of his sublime ability and ball control.
"Alfie has always given 100% and although we are sad to see him move on, he leaves with our thanks and best wishes on his return to the English Football League."
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