Tianti was a native of Killingly, Connecticut, graduated from Plainfield High School, and attended the University of Connecticut and the University of Massachusetts. She was elected president of the AFL–CIO union federation in Connecticut in 1985.
She started her career at the American Thread Company factory in Willimantic, Connecticut in 1956. She later became president of her local union, and from 1962 to 1970 was a union organizer in New England and in the Southern United States. She became the assistant director of the Textile Workers Union of America's Committee on Political Education (COPE), which was the union's political organizing and contributing arm.
From 1970 to 1974, she was an assistant agent for the Connecticut State Board of Labor Relations, and then served as COPE director for the state AFL-CIO. She became the labor federation's secretary- treasurer in 1979.
When the AFL-CIO's Connecticut President John Driscoll retired in 1985, Tianti was elected to succeed him, making her the first woman in the United States to be elected as head of a state labor federation. In 1988, Governor William O'Neill appointed her as the state's first labor commissioner.
- "Betty Tianti Dies At 64". Hartford Courant. 1994-05-17.
- Libov, Charlotte (1987-09-06). "Connecticut Q & A: Betty L. Tianti; 'We Are At A Crossroad In Labor'". The New York Times. Retrieved 2013-08-12.
- "Tribute to Mrs. Betty L. Tianti". Congressional Record. 1994-05-23.[permanent dead link]
- "Betty Tianti". Connecticut Women's Hall of Fame. Retrieved 2013-08-11.