Why do some ventures grow to become dominant market players while most new ventures that do not fail limp along more modest trajectories? In comparison with our knowledge regarding determinants of venture creation or survival, the phenomenon of venture growth has been relatively neglected, both theoretically and empirically. Venture growth is a multi-level phenomenon co-occurring at different analytical and temporal levels. In this chapter we develop a theoretical model that accounts for venture growth as a process, drawing upon the mechanism-based theorizing approach. We offer nine social mechanisms that lead to venture growth, providing a foundation for empirical exploration and further theory building.