The past decade has seen large numbers of migrants from Sub-Saharan Africa attempt to reach Europe irregularly along the dangerous “Mediterranean route”. In response, European governments have invested heavily in initiatives to deter irregular migration, including a proliferation of information campaigns designed to inform potential migrants about the dangers of the journey and the unwelcoming reception they might receive in Europe. There remains little evidence about whether potential migrants actually are misinformed about the risks of the journey and the benefits of Europe. We provide such evidence from representative surveys conducted in 2018 and 2020 in the regional epicenter of irregular migration out of Nigeria. We find that potential migrants in this context are better informed about destination contexts than European information campaigns assume, but are surprisingly poorly informed about the risks of the migration journey itself. We used these results to inform the design of a field experiment implemented in 2020 and 2021 that provides detailed, accurate information about key features of the irregular migration journey to 3000 households across two Nigerian states. We estimate effects of this information on beliefs about migration-related risks, interest in attempting irregular migration, and actual migration from treated households, using data collected approximately six to twelve months after treatment. We identify small but significant shifts in beliefs about risks, in personal interest in attempting the journey, and in actual migration behavior in response to treatment.