Objectives: Sedentary behaviors (too much sitting as distinct from too little exercise) are associated with increased risk of non-communicable diseases. Identifying the prevalence and sociodemographic correlates of sitting time can inform public health policy and prevention strategies. Methods: A population-based national survey was carried out among Omani adults in 2008 (n = 2 977) using the Global Physical Activity Questionnaire, which included a measure of total sitting time. Bivariate and regression analyses examined the associations of total sitting time with sociodemographic correlates (gender, age, education, work status, marital status, place of residence, and wealth). Results: The proportion who sat for ≥ 7 hours/day was significantly higher in older than in younger adults (men: 22.0% vs. 14.6%, p < 0.010; women: 26.9% vs. 15.2%, p < 0.001, respectively). The odds ratio (OR) for prolonged sitting was half for men who were not working compared to those who were (p < 0.050). For younger women, the OR for sitting ≥ 7 hours/day was nearly a third for educated women compared to least educated (p = 0.035). For older women, the OR for prolonged sitting was more than double for married women compared to unmarried (p < 0.001). Conclusions: One in five Omani adults was identified as sitting for prolonged periods, at levels understood to have deleterious health consequences. Higher-risk groups include older adults and working men. With sitting time identified as a key behavioral risk to be targeted for the prevention of non-communicable diseases, further research is needed to understand the factors associated with domain-specific sitting time in order to guide prevention programs and broader public health approaches.