Introduction: The diagnosis of coronary artery anomalies (CAAs) can be challenging due to the highly variable manifestations and symptoms. CAAs occur in less than 1% of the population. Multidetector cardiac computed tomography angiography (CTA) provides excellent spatial and temporal resolution for the imaging of CAAs. This case report describes an anomalous origin of the left main coronary artery. Case presentation: A 64-year-old woman with atypical chest pain underwent coronary CTA. The CT demonstrated that the left coronary artery was originating from the right coronary sinus and had an interarterial course with an approximately 50% stenosis at the segment between the great arteries. Invasive coronary angiography confirmed hemodynamically significant stenosis of the interarterial segment. The patient underwent off-pump coronary artery bypass graft surgery. Conclusion: Left coronary artery originating from the right coronary sinus with an interarterial course increases the risk of sudden cardiac death. In these patients, surgical revascularization is recommended. However, timely diagnosis, especially in those with mild symptoms, remains challenging. Coronary CTA is a robust tool to diagnose CAA and provides valuable information to support the clinical decision making in this patient population.