Prosocial interventions grounded in social interactions have shown limited effectiveness in alleviating depressive symptoms, possibly because of the discomfort and unease that depressed individuals experience during such interactions. We developed and examined an innovative prosocial intervention—an online micro-charitable giving intervention, in which individuals voluntarily donated at least one Chinese cent (¥0.01, or about $0.0014) daily. We conducted three preregistered, 2-month randomized controlled trials with depressed individuals (Sample 1: N = 125, Sample 2: N = 296, Sample 3: N = 462). Results showed that, compared with the waitlist group, the intervention group exhibited significantly greater improvements in both depressive symptoms (Cohen’s ds = −0.19 to −0.46) and emotional positivity (Cohen’s ds = 0.22 to 0.49), and that emotional positivity mediated the intervention’s effect on the reduction of depressive symptoms. Exploratory analysis found a slightly larger intervention effect for generous donors than for minimal donors. This low-cost, easily accessible prosocial intervention holds potential for the prevention of depression. [Box: see text]