There is emerging evidence that Omega-3 polyunsaturated fatty acids (PUFA) supplements can decrease aggression. However, experimental studies with adults from non-specific populations are scarce. We hypothesized that Omega-3 supplements would decrease self-reported aggression among non-clinical participants. In a double-blind randomized trial, two groups of participants (N = 194) aged 18-45 from the general population followed a 6-weeks treatment with 638mg docosahexaenoic acid (DHA) and 772mg eicosapentaenoic acid (EPA) per day or the equivalent quantity of copra oil (placebo). Self-reported aggressiveness was measured at baseline and after the 6-week treatment period. Findings showed that Omega-3 supplements significantly decreased self-reported aggressiveness at the end of the 6-week period (d = 0.31). In conclusion, this experiment indicates that Omega-3 administration has beneficial effects in reducing aggression among the general population.