Tourism-induced disturbance is a growing concern in wildlife conservation worldwide. This case study in a key protected area in Sri Lanka, examined the behavioral changes of Asian elephants in the context of elephant watching tourism activities. Observations of different age–sex-group classes of elephants were conducted focusing on the feeding activity of elephants in the presence vs. absence of tourists. Frequency and duration of alert, fear, stress and aggressive behaviors of elephants were significantly high in the presence of tourists and these behaviors occurred at a cost of feeding time. Tourist behavior, vehicle noise, close distances and time of the tours were closely associated with the behavioral changes of elephants. It is important to monitor tourism effects on endangered species such as Asian elephants and to take proper measures including controlled tourist behavior and vehicle activity in protected areas in order to reduce disturbance of wildlife behavior.