A 94-year-old woman underwent primary percutaneous coronary intervention for a total occlusion of the right coronary artery. A 6-Fr Ikari-left guiding catheter was inserted through the right radial artery. Initially, thrombectomy was performed with a conventional thrombus aspiration catheter. However, only small fragments of thrombus were aspirated and coronary blood flow was still obstructed. Subsequently, a 4.5-Fr straight guiding catheter was advanced through the 6-Fr guiding catheter into the coronary artery and aspiration was reinitiated. During the course of aspiration, the backflow of the blood was blocked. The inner catheter was pulled back slowly, maintaining suction. Just before it reached the tip of the 6-Fr guiding catheter, another vacuum syringe was attached to the side arm of the Y-connecter of the 6-Fr guiding catheter and additional aspiration with the outer guiding catheter was started. After complete retrieval of the 4.5-Fr catheter from the guiding catheter, thrombus was found in the vacuum syringes from both inner and outer guiding catheters. We consider that this double aspiration, with a mother-child catheter technique, is a simple and effective means of aspirating a larger thrombus, and may prevent the dislodgement of thrombus at the tip of the outer guiding catheter, which could cause systemic embolism.