Since no nomination other than Lalu Yadav's was filed, he has been unanimously chosen to the post, RJD National Election Officer Jagadanand Singh told PTI.
Yadav had filed nomination yesterday, Singh said.
Yadav, whose present tenure would be for three years - 2016-19 - will assume the charge formally on January 17.
Lalu Yadav has been RJD chief since its inception in 1997.
Yadav and his supporters had split from Janata Dal to form Rashtriya Janata Dal (RJD) on July 5, 1997, following differences over post of president.