Background Vitamin D deficiency is considered an emerging health problem that affects at least one billion patients worldwide. Calcitriol 1,25(OH) 2 D 3 has several systemic effects, including anti-inflammatory, anti-thrombotic and anti-atherosclerotic impacts that explain its cardioprotective effects. The precise association between vitamin D and its metabolites and the value of supplements in acute coronary syndrome (ACS) is still controversial. This study aims to search the association between vitamin D 2 , D 3 , and metabolites and ACS in patients undergoing coronary angiography. Materials and Methods This was a case–control study on 73 consecutive adult patients with ACS undergoing coronary angiography compared to 50 controls without coronary artery disease and matched for age and sex from June 2019 till July 2019. Echocardiography and coronary angiography were done for all cases. Plasma vitamin D and its metabolites were measured at admission for all participants along with chemistry profiles. Results Vitamin D and its metabolites were statistically significantly lower in ACS patients than the controls. Multivariate regression analysis revealed that low levels of 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH) 2 D) significantly predicted ACS occurrence; the other significant predictors were high systolic blood pressure (BP), high total cholesterol, and low high-density lipoprotein-cholesterol. Interestingly, vitamin D 2 and D 3 did not significantly predict ACS (p>0.05). We did not find a statistically significant association between the number of affected coronary vessels and vitamin D metabolites. Moreover, there was no statistically significant correlation between vitamin D and its metabolites and left ventricular ejection fraction measured by echocardiography. Conclusion There was a strong association between vitamin D and all its metabolites with ACS. Significantly, low 25(OH)D and 1,25(OH) 2 D predicted ACS, but vitamin D 2 and D 3 did not. Large randomized controlled trials are needed to verify the beneficial values of vitamin D supplementation in ACS patients.