Policy projections and recent research suggest that irregular migration flows to Europe will remain a challenge for the foreseeable future. One response by European countries has been to make significant investments in information campaigns designed to discourage irregular departures toward Europe, although the evidence base for these kinds of interventions remains limited. There is in particular virtually no evidence from randomized controlled trials with representative population samples and actual migration as an outcome. We contribute such a study in this paper, analyzing a field experiment we implemented from 2020 to 2023 with 3,200 households in Edo and Delta states in Nigeria, a hotspot of irregular international migration. Treated households received detailed, accurate information about features of the journey along the "Mediterranean route". We estimate effects of this information on beliefs about migration-related risks, interest in attempting irregular migration, and actual migration from treated households. We find significant effects on beliefs and migration intent, in line with the logic of the intervention. We also find that small effects on international migration are surpassed by the intervention’s negative effect on domestic migration, and we discuss implications of this finding for policy.