Umezawa was born in Obama City, Fukui Prefecture, as the second son in a family of seven children.
After serving in the Japanese army during World War II, Umezawa did work on tuberculosis which led to his discovery, in 1955, of the aminoglycoside antibiotic kanamycin.
By this stage Umezawa was heading the Institute of Microbial Chemistry in Tokyo where his main focus was antimicrobial agents manufactured through fermentation processes.
His elder brother, Sumio Umezawa, was a chemist who had sometimes assisted in his work.
[1] The Hamao Umezawa Memorial Museum in Setagaya, Tokyo was named in his honor.