Sambor, 22, joined Atherton in the summer from Witton Albion, scoring the winner in a 2-1 win at Grantham Town in his final game for Brad Cooke's side.
He made 22 appearances for Witton last season, scoring four goals following a move from Cammell Laird early in the campaign.
Widnes joint-manager Kev Towey said: "Kyle is the type of forward we've been after for sometime.
"He can hold it up and run behind which is something we haven't really had since Ben Hodkinson left the club.
"I think based on the showing against Marine you can tell that he's going to fit in really well.
"He's going to be a real handful for us and we're delighted to have him on board."