We present a novel, simple, and low-cost “side-hole” technique for a patient with ST-segment elevation myocardial infarction (STEMI) caused by an occlusion of an anomalous origin of the culprit coronary artery (AOCCA). In a case where standard guiding catheters failed to engage the anomalous left coronary artery (LCA), we created an approximately 3 mm side-hole near the tip of a 5 Fr diagnostic catheter and then introduced a guidewire and microcatheter directly into the anomalous left main trunk (LMT). Subsequently, we withdrew this diagnostic catheter and exchanged it for a guiding catheter over the guide wire, enabling rapid primary PCI. This approach facilitated rapid wire passage, minimized additional device use, and helped reduce overall reperfusion time. It may be especially useful in urgent STEMI cases where a suitable guiding catheter for AOCCA lesions cannot be readily identified.