Paddy Madden spoiled Doncaster Rovers' Boxing Day celebrations with the winner at the Keepmoat Stadium.
Scunthorpe stretched their unbeaten away run to four games after Madden tapped in Luke Williams's left-wing cross.
In the first half, Cedric Evina and Nathan Tyson both hit the side-netting for Doncaster, while Cameron Stewart hit the crossbar late on.
Scunthorpe United manager Mark Robins said: "It's a magnificent way to start the Christmas games, so I'm absolutely delighted.
"It was a great performance, great goal scored and a really good solid away performance.
"The best present you can get is three points."