Kanhar's Kui Samaj Samanwaya Samiti (KSSS) has been spearheading campaign against exploitation of tribals by other caste people in communally sensitive Kandhamal district.
About 200 people earlier supporting Congress and BJD also joined the party along with Kanhar, BJP sources said.
Kanhar, who was earlier supporting Naveen Patnaik led BJD, is the secretary of the coordination committee of the Kui Samaj, a powerful tribal organisation in Kandhamal district that has a large support base in the district.
The ruling BJD, however, said that Kanhar's joining the BJP would not affect its electoral prospect in the ensuing by-elections. "Kanhar was not a member of BJD. His joining the BJP will not affect us," said BJD spkesman Samir Das.