The article examines new firm formation in the old industrial region (OIR) of Bergslagen in Sweden, and in particular the role of in-migrants. The study is based on longitudinal georeferenced microdata (1993–2008) compiled by Statistics Sweden and providing information on individuals' attachments to the Swedish labour market, as well as workplaces and firms, education, income, and family composition. This specially commissioned database enabled the characterization and analysis of emerging forms of entrepreneurship and self-employment, as well as the socio-economics of the labour market. The longitudinal data allowed the authors to trace actions taken by individuals over time. The results indicate that new firm formation is related to private services, rather than to the traditional manufacturing sector and public services that currently dominate the regional labour market. Self-employed in-migrants are active in other sectors than non-migrants, and show some distinct features in terms of their lower age, better education, and more often non-Nordic background. The study showed that both in-migration and return migration had a positive, significant, and substantial effect on migrants' decision to start a business when a number of other individual characteristics had been controlled for.