Background: Vitamin D deficiency is prevailing in Saudi Arabia. Recent national data indicated an inverse association between vitamin D status and coronary heart disease (CHD), which increases concerns about vitamin D deficiency as a serious public health problem. Therefore, the current study aimed to investigate whether knowledge, attitudes and behaviors related to vitamin D contribute to the prevalence of vitamin D deficiency among adults with and without CHD in Saudi Arabia. Methods: This case-control study consisted of 130 CHD cases and 195 matched controls. The study subjects were recruited from three hospitals in Saudi Arabia. Structured interviews were completed to collect data on participants’ socio-demographics, knowledge about vitamin D, attitudes toward sun exposure, and behaviors related to vitamin D. Also, serum vitamin D levels were measured. Results: Severe vitamin D deficiency [serum 25(OH)D < 10 ng/mL] was more prevalent in the CHD cases than in the controls (46% and 3%, respectively). The total knowledge score was higher in the controls than in the cases [2.5 (±1.8) and 1.6 (±2.2), respectively]. The cases had better attitudes toward sun exposure compared to the controls (p = 0.001); however, the controls had better attitudes toward vitamin D compared to the cases (p = 0.001). The controls had a higher consumption of multivitamin supplements than the cases (6.7% and 0.8%, respectively; p = 0. 010). Similarly, the controls had a higher consumption of butter (p = 0.001), oily fish (p = 0.004), and liver (p = 0.003) than the cases; however, the cases had a significantly higher intake of milk (p = 0.001). A multivariate logistic regression showed that vitamin D deficiency [25(OH)D < 20 ng/mL] was associated with low levels of knowledge about vitamin D, with an odds ratio of 1.82 (95% CI: 1.08–3.06, P = 0.024). Vitamin D deficiency was also associated with low intake of vitamin supplements, with an odds ratio of 4.35 (95% CI: 2.12–8.92, P < 0.001). Conclusion: The present study revealed that low levels of knowledge about vitamin D and low consumption of vitamin supplementation, including vitamin D, calcium, multivitamin, and calcium supplements with vitamin D, may have contributed to the higher prevalence of vitamin D deficiency among the CHD cases than among the controls. Further studies using a qualitative approach are crucial to explore the underlying reasons for low knowledge about vitamin D and behaviors related to vitamin D including the intake of vitamin supplementation that may contribute to the high burden of vitamin D deficiency in the country.