[2][3] Tsao was a teacher before she received a scholarship from medical missionary Mary Hancock McLean to attend college in the United States in 1905.

[7] Tsao was an intern under Bertha Van Hoosen at Chicago's Mary Thompson Hospital,[2][8] and her success there opened the door to other Chinese and Chinese-American women physicians, including Margaret Chung.

[9] Tsao returned to China after internships in Chicago and St. Louis,[10][11] then in 1912 took an appointment at a Quaker-sponsored hospital in Nanjing, where she remained until 1918.

While in Nanjing, she was also involved with the Union Training School for Nurses, taught at Ginling College for Women, and gave public lectures on health topics.

[14] Mary Hancock McLean wrote a short biography, Dr. Li Yuin Tsao: Called and Chosen and Faithful (1925).