Background: Nutrition plays a major role in the prevention and management of diet-related disease. With the absence of clinical nutrition dietitians, physicians are considered responsible for prescribing nutritional support. Identifying weaknesses in nutritional knowledge among Saudi physicians may provide guidance to improve their nutritional knowledge. Methods: A cross-sectional study that used an anonymous electronic questionnaire to investigate physicians’ knowledge of the clinical nutrition discipline. In addition to demographics, the questionnaire consisted of 15 questions covering six areas in the clinical nutrition discipline (macro- and micronutrients, nutrition and chronic diseases, nutrition and metabolic diseases, nutrition care process, nutrition support therapy, and research). For continuous variables, independent t-tests and one-way ANOVA were used. Results: A total of 332 had completed the questionnaire and were included in the study. Most of the physicians were Saudi (87%), male (73.5%), aged between 26 and 35 years (63.3%), and without health problems (56.3%). The mean score of the physicians’ knowledge was 5.3 ± 1.97 out of 15. Physicians who reported that they received some sort of nutritional training or course (M = 5.57, SD = 2.08) scored significantly more than physicians who did not (M = 5.10, SD = 1.86); t(330) = −2.174, p = 0.30. Conclusions: Nutrition should be reinforced as an important component of continuing medical education. There is a need for hiring more dietitians in health care settings in Saudi Arabia as an integral part of a multidisciplinary team delivering medical care services.