Dattatreya Bapurao Thengadi was born in Arvi, Wardha, Maharashtra on 10 November 1920. He studied law at Law College in Nagpur.[3] He finished his post-graduation from Morris College and LLB from Law College in Nagpur. He was a lawyer as well as a philosopher, and displayed an early talent for administration. At the age of 15, he served as president of the "Vanar Sena" as well as the Municipal High School student union at Arvi.[4] He took part in India's Freedom Movement and was a member of the Hindustan Socialist Republican Association (HSRA) from 1936–38. He became a full-time pracharak in 1942.
He worked as organizing secretary of the Indian National Trade Union Congress (INTUC) from 1950–51, and was associated with the Postal & Railway Workers Union (Communist Party).[4] He was organising secretary of the Bharatiya Jana Sangh for Madhya Pradesh (1952–53) and South India (1956–57).
Thengadi was a member of the Rajya Sabha from Bharatiya Jana Sangh for two terms during 1964–76,[8] also served as its vice-chairman in 1968–70. He organized protests during the anti-Emergency movement in 1975.