We study the impact of the large inflow of Ukrainian refugees into Poland following Russia’s 2022 invasion on business creation. Ukrainians registered 38,833 firms in Poland in 2022–23, accounting for 7% of all new registrations. We first document the role of refugees behind this wave of businesses and then show that new Ukrainian businesses stimulate Polish entrepreneurship. Using an identification strategy based on refugee shocks across counties and Ukrainians’ comparative advantage across sectors, we find that 10 extra Ukrainian registrations lead to 3.4 to 5.3 more Polish firms.