Risk perception and individual reactions to risk are not necessarily comparable, and socioeconomic status may affect individual reactions to risk. This study aimed to investigate the association between socioeconomic status and reactions to radiation exposure risk. This cross-sectional study, based on a self-reported online survey was conducted between 3 March and 21 March 2012, one year after the accident at Fukushima Daiichi nuclear power station. We used feelings of anxiety and risk-averse behavior concerning radiation exposure as dependent variables, and equivalent income and educational attainment as independent variables. Multiple logistic regression analysis was applied to estimate adjusted odds ratios (aORs) and 95% confidence intervals (95% CIs) with adjustment for possible confounders. Among 10 000 participants, 23.0% felt anxious and 12.0% engaged in risk-averse behavior for radiation exposure. Participants with a higher socioeconomic status tended not to feel anxious but undertook risk-averse behavior. Participants in the highest quartile income category did not report feeling anxious but showed prevalent undertaking of risk-averse behavior for radiation exposure compared to the lowest income category (for anxiety, aOR, 0.77; 95% CI, 0.64-0.93, for risk-averse behavior, aOR, 1.33; 95% CI, 1.04-1.69). University or graduate-school graduates were associated with greater risk-averse behavior compared to junior high school or high school graduates (aOR, 1.49; 95% CI, 1.29-1.73). Socioeconomic status may affect reactions to radiation exposure risk. Risk communication strategies should consider the socioeconomic status of those affected.