Psoralidin (Pso) is a coumestan-type compound found in Psoralea corylifolia L. that exhibits a broad spectrum of pharmacological properties. The current work aimed to study, for the first time, the antioxidant capacities of Pso under physiological circumstances. Tandem experimental and computational approaches were used to fully understand the interaction of Pso with ROS (reactive oxygen species) at the molecular level as well as its impact on the basal ROS level in cells. Pso has been found to be a potent radical scavenger in physiological polar media, acting via the single electron-transfer mechanism rather than the hydrogen-transfer mechanism. In contrast, Pso is a moderate radical scavenger in lipid media, and its reaction is determined by hydrogen transfer from the 7OH group. The in vitro assays revealed that Pso moderately reduces the basal ROS level in human keratinocytes at non-toxic concentrations, which is in agreement with the computational study. These findings indicate that Pso is a promising antioxidant, but in its natural form it has no significant effects on basal cell conditions.