Objectives: This study aimed to investigate the lifestyle habits—physical activity (PA), eating habits (EH), and sleep duration (SD)—of Omani adolescents, and to examine gender differences in such variables. Methods: 802 Omani adolescents (442 females and 360 males), aged 15‒18 years were randomly recruited. Anthropometric indices, PA level, and EH and SD were evaluated by the Arab Teenage Lifestyle questionnaire. A semi-quantitative food frequency questionnaire for dietary assessment was also administered. Results: The results showed that although the study subjects had a sedentary lifestyle (lack of PA, average of 6.7 hours sleep, and consumption of high calorie foods), they maintained a normal body mass (less than 25 Kg/m2 ). Males were more than twice as active as females. With respect to EH, there were few gender differences, except in dairy and meat consumption where 62.5% and 55.5% of males consumed more than 3 servings, respectively, compared to 18.78 % and 35.2% of females, respectively. In addition, waist/height ratio, height, reasons for being active, energy drinks, potato consumption, eating sweets, vigorous PA and breakfast EHs were statistically significant independent predictors for BMI, P <0.05 for both males and females. Conclusion: This study revealed a high prevalence of sedentary behaviors and a low level of physical activity, especially among females. Unhealthy dietary habits were also widely found among both genders. There is an urgent need for more research as well as a national policy promoting active living and healthy eating and discouraging sedentary behaviour among Omani adolescents.