Gudmundsson already had a yellow card when he received a second one during first-half stoppage time, after a late challenge on Crystal Palace's Ismaila Sarr.
Referee Thomas Bramall seemed to have forgotten that the Swede had already received a yellow card, but after the home side's players drew Bramall's attention, he showed Gudmundsson a red card.
Leeds thus had to manage without their full-back and play a man down throughout the second half, but managed to hold off Crystal Palace, and the match ended 0–0. An important point for Leeds in the fight to avoid relegation.
Gudmundsson is expected to be part of Sweden manager Graham Potter's squad for the World Cup playoff against Ukraine on March 26.
Meanwhile, Manchester United won 3-1 in the top-of-the-table clash with Aston Villa and solidified their position in the top three.
