A climate change adaptation is the solution of preventing the impacts of climate change on agriculture. The Kosi River is also known as the sorrow of Bihar in India. Based on an exploratory research design, this study, purposively selected in the flood-affected region of Bihar, examines their adaptive behavior towards climate change in the Araria, Katihar, Kishanganj, and Purnea districts. A total of 400 respondents were randomly selected from two blocks in each district, two clusters villages from each blocks and 50 respondents in each cluster villages. A well structured and prior tested interview schedule was used to interview the respondents. The main objective of the study was to compare the adaptive behaviour of farmers towards climate change in Kosi region of Bihar through suitable statistical method. Post Hoc Tukey's Honestly Significant Difference (HSD) test was used to compare the adaptive behavior of farmers among the district. According to the results, Purnea (x̄=97.83) had the highest adaptive behaviour capacity of farmers towards climate change, followed by Katihar (x̄=90.73), Araria (x̄=83.06) and Kishanganj (x̄=79.77). Thus, through Post Hoc test making 6 districts for pair of comparison. Based on a hypothesis that farmers in the Kosi region of Bihar are not differently adaptive to climate change, post-hoc Tukey's HSD test was used to test this hypothesis. Tukey's HSD test, Purnea (3) has the maximum number of stark and significant differences with all three districts, i.e., significant at the 1% level with Katihar, Araria and Kishanganj when it is used as a reference category. As a result of this study, farmers of Kishanganj district has least adaptive behavior capacity towards climate change, which suggests that climate change training and awareness programmes are needed for the improvement in adaptive behaviour of farmers.