The present study illustrates the inclusive information of morphological relationships, including morphometric parameters, meristic count, length-length relationships (LLRs), length-weight relationship (LWRs) and feeding biology of two threatened freshwater fish species, Glossogobius giuris and Nandus nandus from Sessa River, Dibrugarh, Assam. All the morphometric parameters revealed a proportional change with the increase in total length of the fish species. The growth coefficient ‘b’ in the LWR for both the fish species G. giuris and N. nandus exhibited values <3 which shows a negative allometric growth. The coefficient of correlation (r) was recorded 0.97 in G. giuris and 0.95 in N. nandus which showed high degree of correlation in the species. The relative condition factor (K) fluctuated between 1.79 and 1.97 respectively, indicating a state of well-being for these fish species. The degree of association between the variables was computed by the determination coefficient, R2. The body lengths were found highly significant with all “r” values being >0.900 and positively correlated with TL. The value of RLG for both the species was <1 which indicates the carnivorous nature of the fishes.