To assess primary care physicians' (PCPs) knowledge and attitudes toward sleep disorders. Methods: In this cross-sectional quantitative study, we surveyed 88 primary care centers under the Ministry of Health during 2015 in Riyadh, Saudi Arabia, using a combination of pre-designed validated questionnaires. Knowledge was assessed using the Assessment of Sleep Knowledge in Medical Education (ASKME) questionnaire, and attitude was assessed using a pre-designed survey. For numerical variables, t-test was used, and for categorical variables, Chi-square test was used. Results: Data from 223 PCPs (males 50.2%) were analyzed. Among the participants, 44 (19.9%) did not know that sleep medicine is a distinct medical specialty, and 24 (10.9%) felt that sleep disorders are uncommon medical problems based on their daily practice. Only 87 (39%) of physicians stated that they referred patients with sleep disorders to specialized medical centers for further management. The mean score of the ASKME questionnaire was 14.4 ± 4 out of 30 (48%). The majority of physicians (78.5%) obtained a score between 11 and 20. Score results were not related to gender or years of practice. Conclusion: Primary care physicians' have a low level of awareness and poor knowledge of sleep medicine and sleep disorders.