The National Executive of Bihar-based party held its meeting where Paswan (68), who is a Union minister, was elected its president, a party statement said.
LJP is a BJP ally and has six Lok Sabha MPs but no MLA.
The party draws its strength from Paswan's appeal among a section of Dalits in the eastern state.
Seen as a keen reader of political winds, Paswan has been heading the party since its inception and has joined hands with national parties across the ideological spectrum.