1995-2010

As a member of the RJD, Sadhu Yadav was a MLC in Bihar Legislative Council from 1995 to 1997 and 1998 to 2000 and was also MLA of Gopalganj in Bihar Legislative Assembly from 2000 to 2004. He was elected in 14th Lok Sabha as a Member of Parliament (MP) for the Gopalganj Lok Sabha constituency.^{[8][9][10][11][12][13]}

He left the RJD after a dispute with his brother-in-law,^[14] Lalu Prasad Yadav, related to the allocation of constituencies between RJD and the Lok Janshakti Party (LJP). The Gopalganj constituency had become a reserved seat then and Prakash Jha an LJP candidate, who had lost the election in 2004 from Bettiah, was preferred for the Paschim Champaran seat.^[11][15]

Two days after leaving the RJD, in March 2009, Sadhu Yadav joined the Indian National Congress (INC) and unsuccessfully contested the Paschim Champaran Lok Sabha constituency and lost to Sanjay Jaiswal.^[15][16]

2010-Present

In March 2010 he was briefly suspended from the Indian National Congress^[17] for allegedly challenging the party's policy strategy. He denied voicing any such challenge and his explanation was accepted.^[14][18] Returning to the Gopalganj constituency, Yadav then fought and lost as a candidate for the INC in the 2010 Bihar legislative assembly election.^[19][20] That election saw confusion regarding the ages of several candidates, including Yadav. The candidates claimed that errors had resulted in the printing process for pre-election affidavits, and in Yadav's case this meant that he was recorded as aged 47 in 2009 when he had been shown as 44 at the time of the 2004 general elections. When asked for clarification by the BBC in 2009, he claimed to be aged 40.^[21]

On 25 March 2014, he announced his candidature for 2014 Lok Sabha elections from Saran contesting against his sister and ex-Chief Minister of Bihar Rabri Devi. He stood as an independent candidate.^[22] However, he lost the seat to BJP candidate Rajiv Pratap Rudy. He finished a distant third from the Barauli assembly seat in 2015 assembly polls by Jan Adhikar Party (Loktantrik).^[23] He contested the 2019 Indian general election as a BSP candidate from Maharajganj, but lost to Janardan Singh Sigriwal.