The process for blood donation is considered safe, but some adverse events have been reported. Risk factors for adverse events were assessed in this study.A retrospective case-control study was conducted to investigate the risk factors for adverse events after blood donation between 2010 and 2013. Variables such as gender, age, body mass index (BMI), donation status, donation volume, donation site, pre-donation systolic blood pressure (SBP), and pre-donation diastolic blood pressure were compared between donors with and without adverse events. Multiple logistic regression analysis was performed to assess the joint effects of age, gender, and donation status on adverse events.The incidence of adverse events among adult blood donations was 1287/1,253,678 (0.1%). On multivariate logistic regression analysis, blood donors aged <35 years (odds ratio [OR], 2.99, 95% confidence interval [CI], 2.57-3.48), of female gender (OR, 3.30, 95% CI, 2.62-4.15), and with first-time donor status (OR, 6.40, 95% CI, 5.17-7.93), donation of 500 mL (OR, 2.22, 95% CI, 1.83-2.69), predonation SBP <124 mm Hg (OR, 1.25, 95% CI,1.05-1.48) and BMI <24 kg/m (OR, 1.67, 95% CI, 1.42-1.96) were associated with increased likelihood of adverse event. Further analysis with joint effects method revealed that first-time female donors aged <35 years are associated with the highest odds of adverse events when compared with repeat male donors aged ≧35 years (OR, 100.57, 95% CI, 48.45-208.75).The findings of our study should prove useful in identifying donors at risk and planning appropriate strategies for the prevention of adverse effects.