The aim of this study was to investigate the risk factors for access site-related complications after transradial coronary angiography (CAG) or percutaneous coronary intervention (PCI). Transradial PCI has been shown to reduce access site-related bleeding complications compared with procedures performed through a femoral approach. Although previous studies focused on risk factors for access site-related complications after a transfemoral approach or transfemoral and transradial approaches, it is uncertain which factors affect vascular complications after transradial catheterization. We enrolled 500 consecutive patients who underwent transradial CAG or PCI. We determined the incidence and risk factors for access site-related complications such as radial artery occlusion and bleeding complications. Age, sheath size, the dose of heparin and the frequency of PCI (vs. CAG) were significantly greater in patients with than without bleeding complications. However, body mass index (BMI) was significantly lower in patients with than without bleeding complications. Sheath size was significantly higher and the frequency of statin use was significantly lower in patients with than without radial artery occlusion. Multiple logistic analysis revealed that sheath size [odds ratio (OR) 5.5; P < 0.05] and BMI (OR 0.86; P < 0.01) were risk factors for bleeding complications; and sheath size (OR 5.2; P < 0.05) and the lack of statin pretreatment (OR 0.50; P < 0.05) were risk factors for occlusive complications. In conclusion, these findings indicate that down-sizing of the devices used in transradial procedures might attenuate access site-related complications after transradial CAG or PCI. Statin pretreatment might also be a strategy that could prevent radial artery occlusion after transradial procedures.