Yadav, a three-term RJD MLC, was given primary membership of the party by its state unit President Mangal Pandey at a function held in the party office here.
In addition to him, a Bhagalpur-based doctor NK Yadav and Anand Mandal, kin of the late socialist leader BP Mandal, also joined the saffron party.
Speaking on the occasion, Yadav said he believed in the BJP ideology and asserted he would work hard as a committed member of the party in its mission to bring NDA to power under the leadership of Narendra Modi.