B. P. Mandal was raised in the village of Murho, in the Madhepura District (formerly Saharsa District) of northern Bihar. B. P. Mandal received his early education in Madhepura and he attended Raj High School in Darbhanga. He matriculated at Patna College in the 1930s and worked as an Honorary Magistrate from 1945 to 1951. B. P. Mandal and his wife, Sita Mandal, were survived by five sons and two daughters. The third son, Maninder Kumar Mandal, and his son Nikhil Mandal in national and state politics.
B. P. Mandal was the son of Ras Behari Lal Mandal, a wealthy zamindar. According to local legend, his father raised the demand for Indian independence at the 1911 Delhi Durbar. Ras Behari Lal Mandal later made his contribution as founder of All India Gope Jatiya (Yadav) Mahasabha and was one of the few zamindars who laid the foundation of Indian National Congress in Bihar. His eldest son Bhubneshwari Prasad Mandal became Member of Bihar-Orissa Legislative Council in 1924 and was Chairman of Local Board, Bhagalpur till his death in 1948. Ras Behari Lal Mandal’s second son, the British arrested Kamleshwari Prasad Mandal along with Jai Prakash Narain and others and lodged in Hazaribagh Central Jail , and became M.L.C. in Bihar in 1937. B. P. Mandal was the youngest of the three sons of Ras Behari Babu.
His political career began with the Indian National Congress but he joined the Janata Party after the Emergency Period. Later in his political career, B.P. Mandal gravitated toward socialist political ideas and he eventually joined the Samyukta Socialist Party. B. P. Mandal became Chief Minister of Bihar in 1967-68 for a short period before his Government was pulled down by supporting Congress Party for not rewinding the Commission appointed to ask into allegations of corruption against Congress leaders during previous government.
Mr B. P. Mandal was a Member of Parliament in the Lok Sabha for the state of Bihar from 1967 to 1970 and 1977 to 1979. He was also the Chief Minister of Bihar for forty-eight days in 1968, a period of intense political instability (his predecessor was Chief Minister for only three days). In December 1978, Prime Minister Morarji Desai appointed a five member civil rights commission under the chairmanship of B. P. Mandal. The commission’s report was completed in 1980 and recommended that a significant proportion of all government and educational places be reserved for applicants from the Other Backward Classes. The commission’s report was tabled indefinitely by Prime Minister Indira Gandhi. A decade later, Prime Minister V. P. Singh implemented the recommendations of the Mandal Report.
The Government of India issued a stamp in honor of B. P. Mandal in 2001. A college named in his honor, B. P. Mandal Engineering College, was founded in 2007.