Town went into Sunday’s clash at Derwent Park having won their opening three games.
But they were frustrated by some incredible Doncaster defending as Richard Horne’s side took their record to three wins from four.
The Dons produced a brilliant opening 40 minutes to build a 16-0 lead before they defended heroically to stave off an inevitable Workington onslaught.
Brad Foster and Sam Smeaton were both sin-binned during the opening exchanges but the 11 men held firm before tries from Ross Peltier, Matty Beharrell and Tom Halliday put Doncaster in the box seat at the break.
Town came back out with the bit between their teeth and they were level at 16-16 after 54 minutes.
Alex Holdstock went over from the next set and Beharrell kicked the conversion and two penalties to nudge the visitors back into a 26-16 lead.
Caine Barnes’ try reduced the deficit to six points with ten minutes to play and Workington built up a head of steam but came up against a resolute defence.
Joe Brown did find a way over in the 79th minute to close the gap to two points but Carl Forber failed to convert and the Dons held on for a confidence-boosting victory.