Social enterprises are profit-making businesses which trade for a social purpose. They bridge the gap between welfare and work, providing employment opportunities for disadvantaged groups often excluded from employment in the construction industry. Social enterprises are a fast-growing part of a larger third economic sector. However, compared to other industries, there are relatively few social enterprises operating in construction and little is known about the challenges they face in doing so. In-depth interviews at 12 UK social enterprises reveal that many of the challenges faced by social enterprises in the construction industry are similar to those faced by social enterprises operating in other industries. These include: building trust, managing hybridity; securing finance; measuring social impact; and achieving scale. However, in addressing the lack of sector-specific insights in social enterprise research, challenges unique to construction are also identified. These include: procurement practices which favour industry incumbents; costly tender bureaucracy; established supply chain relationships; lack of experience of working with social enterprises; disingenuous corporate social responsibility practices; and fear that social enterprises will reduce competitiveness. Recommendations are made to resolve these challenges, enabling the construction sector to create an ecosystem where social enterprises can thrive. Questions to guide future research into this unexplored area are also proposed.