The Grivet monkey (Chlorocebus aethiop aethiops) is an old-world primate Monkey species distributed on the east of the White Nile in Sudan to Ethiopia, Eritrea, and Djibouti. The study on activity patterns and feeding habits of Grivet Monkeys in and around Wondo Genet College of Forestry and Natural Resource was carried out from February 2021 to August 2022 during both the wet and dry season. Instantaneous scan sampling method was used at 15-min intervals for up to 10 minutes duration. During each scan, individuals were recorded as performing one of the following activities: feeding, moving, resting, grooming, playing, and others. Descriptive statistics and inferential statistics such as One-way ANOVA, Kruskal Wallis test, and Mann-Whitney U-test were used to analyze data.On average, the greatest proportion of the activity time budget of the grivet monkey was devoted to feeding (29.5±0.6%), followed by resting (27±0.8%), moving (26±0.2%), grooming (9±0.2%), playing (5.5±0.6%) and the least time spent on other social activities (3±0.2%). They feed 42 food sources grouped into 41 plant species and one insect. On average, the forb of leaf 32±3.2% comprised the highest percent proportion of their diet, whereas, roots (0.3±0.2%) and insects (0.5±0.4%) comprised the least. Psidium guava was the top preferred plant species and Callistemon linearis was the least preferred plant species by the grivet monkey. Due to the existence of low quality of food in human dominated area, Grivet monkey most of their time spent on feeding activity. Therefore, concerned body and regional governments need to take action to stop deforestation of the natural forests and sustainable management must be needed for the top preferred plant species. Keywords/ Phrase: Activity, Behavior, Proximate analysis, Time budget.