Objective: Young-adult American veterans are at risk for problematic alcohol use. However, they are unlikely to seek care and may drop out from lengthy, multicomponent treatments when they do get care. This randomized controlled trial tested a very brief alcohol intervention delivered over the Internet to reach the population of young-adult veterans to help reduce their drinking. Method: Veterans (N = 784) were recruited from Facebook and randomized to either a control condition or a personalized normative feedback (PNF) intervention seeking to correct drinking perceptions of gender-specific veteran peers. Results: At immediate postintervention, PNF participants reported greater reductions in their perceptions of peer drinking and intentions to drink over the next month, compared with control participants. At 1-month follow-up, PNF participants reduced their drinking behavior and related consequences to a significantly greater extent than controls. Specifically, PNF participants drank 3.4 fewer drinks per week, consumed 0.4 fewer drinks per occasion, binge drank on 1.0 fewer days, and experienced about 1.0 fewer consequences than control participants in the month after the intervention. Intervention effects for drinks per occasion were most pronounced among more problematic drinkers. Changes in perceived norms from baseline to 1-month follow-up mediated intervention efficacy. Conclusion: Though effects were assessed after only 1 month, findings have potential to inform broader, population-level programs designed for young veterans to prevent escalation of drinking and development of long-term alcohol problems. Given the simplicity of the PNF approach and ease of administration, this intervention has the potential for a substantial impact on public health.