At the delayed 2020 Tokyo Olympics, Mu won two gold medals in the Women's 800 meters and Women's 4 x 400 meters relay. She broke the American Women's 800 meter record with a 1:55.21 performance and ended a 53-year Olympic win drought for the USA - the last American who won 800m was Madeline Manning in the 1968 Summer Olympics. Mu had qualified for these Olympics at the US Olympic trials held in Eugene, Oregon by placing first with a time of 1:56.07 in the 800 meters, a world-leading time and the 2nd fastest result in American history. She later broke her own record at the Prefontaine Classic, finishing in 1:55.04 and setting new American and meet records.