Naga People's Front MLA T Torechu died at a hospital in Dimapur on Monday after a prolonged illness.
He was 70 and is survived by his wife and seven children.
Torechu represented Pungro-Kiphire Assembly seat in Kiphire district of Nagaland for four consecutive terms since 2003.
He held various posts in the state government. However, in the present House he was in the opposition.
A state funeral will be held on Tuesday.
Chief Minister Neiphiu Rio and Assembly Speaker Sharingain Longkumer condoled his death.