BJP General Secretary in-charge of Assam Vijay Goel told reporters that party president Nitin Gadkari has appointed Sonowal as the Assam unit chief. His predecessor Ranjit Dutta had resigned earlier citing poor health.
Assembly elections in Assam are still three years away in the state.
BJP got a drubbing in the 2011 Assembly elections in Assam. Its behind-the-scene talks with AGP to put together a post-poll alliance had also come a cropper as both the parties were not in a position to cross the tally of seats secured by Congress.
Sonowal is a former MP from Dibrugarh and a former MLA from Moran seat of Assam. He won both these polls on an AGP ticket. He has also been head of All Assam Student Union (AASU).
Sonowal had gained prominence for filing a petition in 2005 challenging the IMDT Act. A three-judge bench of the Supreme Court had struck down the Act on July 12, 2005.