Floyd (7-8) didn't allow a runner as far as third, handcuffing the Blue Jays on four hits and two walks while striking out three.
The left-hander tossed 61 of his 100 pitches for strikes while winning the for the third time four starts for the American League Central-leading White Sox, who racked up their fifth straight triumph.
Matt Thornton recorded the final four outs for his second save.
Youkilis smacked a two-run homer in the fifth inning for the game's only runs, knocking his third long ball in five games.
Blue Jays starter Ricky Romero (8-4) was tagged with the loss, surrendering two runs on four hits in a six-inning effort.