Hoolock gibbons have been described as highly specialized and selective feeders but largely dependent on ripe sugar, rich juicy fruits and figs in protected as well as anthropogenic influence (non-protected) forest ecosystem. We investigated the dietary preferences of Hoolock leuconedys in protected and non-protected habitats of Lower Dibang Valley district of Arunachal Pradesh, Northeast India. Five groups of H. leuconedys were selected in protected and non-protected forests for intensive study of feeding behaviours. A scan sampling method was employed and a single focal animal has been recorded on the instant every 5 minutes recording feeding activity. Study groups were recorded to feed upon 37 and 28 plant species in protected and non-protected forest respectively. Time spent on feeding figs was found maximum in non-protected forest (43.25%), followed by young leaf (32.97%), other (11.12%) and mature leaves (7.27%). Non-fig fruits contributed minimum (5.39%) in the diet of gibbon’s groups studied in non-protected forest. On the contrary, non-fig fruits and figs contribute almost equally in protected forest (non-fig fruits: 25.26%; figs: 28.09%). Furthermore, precipitation (monthly rainfall) has also been contributed significantly on non-fig fruit feeding in protected forest (Linear regression analysis: R=0.74; F=11.83; p<0.05). Simultaneously rainfall also effects the feeding time on figs (R=0.59; F=5.41 and p<0.05) and mature leaves (R=0.78; F=14.82 and p<0.05). Alstonia scholaris was found as most selected plant species ranking at the top of the selectivity list, whereas the feeding frequency was recorded highest for Ficus hispida. However, 5 plant species were common in both protected and non-protected forests (Alstonia scholaris, Ficus hispida, Castanopsis indica, Ficus hirta, Erythrina stricta). Dietary diversity and the use pattern of different plant species to obtain food are considerably different in both habitats. Thus the present study reveals the importance of some food plant species for conservation and management of population of H. leuconedys and its habitats in the study area as well as others anthropogenic influenced forest areas in northeast India.