Business Angel Networks (BAN) are public or private organizations designed to create a communication channel between business angels and young companies. So far, little is known about the organization and success of BAN. This study develops a theoretical framework for examining the organization and success of BAN based on club theory and the theory of two-sided markets. The theoretical predictions are subjected to extensive qualitative and quantitative statistical analyses in the context of two empirical studies at the BAN and business angel levels. This work thus provides an exciting insight into the functioning and success of BAN for both research and practice (business angels, capital-seeking companies, and public authorities).