Dennis Chavez was born in Los Chaves, Valencia County, New Mexico, on April 8, 1888. He left school at the age of 13 to work as a grocery clerk and later worked in the city's department of engineering. As a result of acting as a Spanish interpreter for Senator Andrieus A. Johns, Chavez came to Washington, serving as a clerk in the Office of the Secretary of the United States Senate from 1917 to 1920. He graduated from Georgetown University Law School, was admitted to the bar in 1920, and returned to Albuquerque to practice law.

He began his political career in the New Mexico House of Representatives in 1923. He was a member of the Democratic National Committee from 1933 to 1936, a member of the U.S. House of Representatives from 1931 to 1935, and an unsuccessful candidate for the United States Senate in 1934. In 1935, Chavez was appointed to the Senate to fill the vacancy left by the death of Bronson M. Cutting. Elected to that seat in 1936, he served until his death.

Chavez supported the New Deal and championed the rights of American Indians and Puerto Ricans. He worked for reciprocal trade agreements, especially with Latin America. He was known for his legislation establishing the federal Fair Employment Practices Commission along with various child care programs. He died in Washington, D.C., on November 18, 1962, and was interred in Albuquerque.