Dorothy Kenyon was born in 1888 in New York City. She was the first of three children. Her father was a patent attorney and she grew up well off.
Kenyon attended Smith College, graduating in 1908. She spent the next several years traveling and enjoying life, then enrolled in New York University School of Law in 1914. She graduated from law school in 1917. She worked as a researcher advising lawyers at the Versailles Peace Conference for her first post-graduate job. She was also known in the 1920s for her support of access to birth control for all women and labor rights.
In 1930, Kenyon opened a private practice with another female lawyer, Dorothy Strauss. In 1939, she left the practice to become a municipal court judge. From 1938 through 1943, she served on the League of Nations Committee to Study the Legal Status of Women, a commitment she followed with membership on the United Nations Committee on the Status of Women from 1946 to 1950.
During the McCarthy trials of the 1950s, Kenyon was accused of involvement with more than 20 Communist organizations. Charges against her were dropped. Kenyon worked as a lawyer for the ACLU and the NAACP in the 1950s and 1960s, and was involved in the fights for Civil Rights and against the Vietnam War.
Dorothy Kenyon died in 1972.