The wild water buffalo-WWB (Bubalus arnee) holds a significant ecological role within Koshi Tappu Wildlife Reserve, Nepal. Despite its importance, there has been a lack of comprehensive research addressing its distribution, habitat suitability, and interaction with domestic cattle. To address these gaps, this study was undertaken with the primary objectives of elucidating the population distribution of B. arnee within the reserve, mapping its habitat suitability, and evaluating the interplay between B. arnee and domestic cattle in the Koshi Tappu Wildlife Reserve. The study area was subdivided into cells to gather data on B. arnee presence using various indicators such as sightings, dung, and footprints. Interaction between B. arnee and domestic cattle was assessed based on their spatial overlap within and outside a 500-meter radius from observation points. Employing the MaxEnt algorithm, distribution data of B. arnee and climatic variables including maximum and minimum temperatures, mean temperature, and rainfall were analyzed, while land use and cover maps were acquired from the Department of Survey for further analysis. Results revealed a concentration of B. arnee in the southwest region of the Koshi Tappu Wildlife Reserve, with a total of 405 individuals recorded, comprising 26 calves, 6 sub-adults, and 373 adults. The distribution pattern displayed a prevalence of small-sized herds (1–15 individuals) followed by medium-sized (15–29 individuals) and large-sized (29+ individuals) herds. Notably, B. arnee presence was most prominent in grassland areas (approximately 49% of observations), while forested regions accounted for the lowest presence (approximately 10% of observations). Interestingly, domestic buffalo were observed near B. arnee only in a single cell in the southwest section of the study area, while in the eastern cells of the reserve, overlaps between domestic cows and B. arnee occurred within a 500-meter radius. Our study indicated a suitability index greater than or equal to 0.5876, encompassing only about 14% of the reserve's total area. The jackknife test highlighted the influential environmental variables in the model, with annual precipitation contributing around 60.8% and the maximum temperature of the warmest month contributing about 39.20% in determining the distribution of B. arnee. The results underscored the significance of annual precipitation, with a regularized training gain of 0.50, compared to 0.32 for the maximum temperature of the warmest month. In conclusion, this study sheds light on the distribution, habitat suitability, and interaction dynamics of B. arnee within the Koshi Tappu Wildlife Reserve, offering valuable insights for informed wildlife management and conservation strategies.