At the 2020 Summer Olympics in Tokyo, Japan and postponed to 2021 due to the COVID-19 pandemic, Milák won the gold medal in the 200 metre butterfly in a new Olympic record time of 1:51.25. He also won the silver medal in 100 metre butterfly in a time of 49.68. His swim set a new European record in the event and moved him up in global rankings to second fastest swimmer in the event internationally thus far, behind Caeleb Dressel and ahead of Michael Phelps.