Swayne’s Hartebeest (SHB) is an endangered endemic animal to Ethiopia. However, its activity pattern and social behavior are not well documented. Hence, we investigated the diurnal activity pattern and social behavior of SHB in the Maze National Park. Data were collected by direct observation of focal-animal from October 2018 to April 2019 and analyzed using descriptive statistics and X2-test. A total of 1004 observations were made for activity pattern study. The SHB were performing four major activities (remain standing: 37.6%, grazing: 32.9%, walking: 15.7%, lying: 11.2%) showing significant differences in the total observation frequencies (X2 = 205.69, P < 0.05). Standing was the dominant activity followed by grazing in the wet season and vice versa in the dry season. Observation frequency for standing showed significant difference between seasons (X2 = 6.614, P < 0.05). Observation frequency for the activities within season (wet season: X2 = 120.6, P < 0.05; dry season: X2 = 100.38, P<0.05) showed variation. A total of 951 observations were made for social behavior study. We found significant differences in the total observation between types of social groups (X2 = 109.52, P<0.05) and between seasons (X2 = 22.722, P<0.05). Female SHB with young calf showed the dominant vigilant behavior. The findings revealed a decrease in the rate of occurrence for vigilance behavior with increasing social group size. We suggest the management plan of the park shall consider the findings of this study as a useful input for sustainable conservation of this endangered endemic species. Key words: Social organization, Swayne’s hartebeest, time budget, vigilance.