A study was carried out to explore indigenous knowledge on utilization of available plant biodiversity which have been utilized for treatment and cure of human ailment by eight Naga tribes i.e. Angami, Zeliang, Ao, Lotha, Sangtam, Konyak, Chakhesang, Rengma, and Khiamniungam in 20 villages of 9 districts of Nagaland during 2005-2010. Selected villages and households were surveyed and interviewed by using the structured schedule (questionnaires) for medicinal plant resources, their uses and information about their relationships with indigenous people. Information about traditional practices adopted for the medicinal resources was also gathered from the 'Local Medicine Men/Local Healers', Goanburha (Village Head Man), village elders etc. About 241 plant species belong to 142 families were recorded for traditional medicine used by eight Naga tribes. Highest number of utilization of medicinal plants were reported from cold regions (22.61%) i.e. from high altitude areas of the state, followed by warm areas (25.73%). Extraction of traditional medicines was highest in case of plant leaf (106 plant species) followed by roots (58 plant species), fruits (45 plant species), whole plant (36 plant species), bark (30 plant species) and the seeds (27 plant species) while the least used part were flowers and pods (21 plant species). About 33 plant species were recorded to use for treating dysentery, followed by 20 plant species for treatment of cough and control fever each. Fifteen plant species recorded for treatment of diarrhoea and 12 plant species were recorded to use for treat asthma. It was also observed that some endangered plant species such as Rhus semialata Murr, Aquilaria malaccensis Lam, and Cephalotaxus griffithii Hook.f., are utilized the people of Nagaland for medicinal purpose.