Background: Knowledge is a critical input for solving sustainable resource management issues. The study was conducted to determine the factors that influence the knowledge and attitudes of fishers about fish diversity and conservation in the Siang River of Arunachal Pradesh. Methods: This study used a descriptive research design. The data were collected from randomly selected 90 respondents from two blocks of East Siang District of Arunachal Pradesh with the help of a structured interview schedule and participant observation technique. The knowledge levels of the fishers were measured under three domains: conservation strategies, reservoir ecology and fishing practices. Result: The findings of the study revealed that the majority (53.33%) of respondents had a medium level of knowledge in three domains. Correlation analysis revealed that fishing experience and annual fishing days were positively and significantly correlated with knowledge level at a 1 per cent level of probability, whereas age and annual income were positively and significantly correlated with knowledge level at a 5 per cent level of probability. Gender, caste, education, family size, family type, average monthly catch and average fishing duration were not associated with the knowledge level of respondents about fish diversity and conservation. The attitude level of respondents was categorized into three categories: positive, neutral and negative. The findings of the study indicated that the majority of respondents (63.33%) had positive attitudes towards fish diversity and conservation, whereas 23.33 per cent had neutral attitudes and 13.34 per cent had negative attitudes toward fish diversity and conservation.