The aim of this article is to theorise the business model innovation (BMI) phenomenon as we explore why and how BMI occurs, specifically to answer the question, What are the mechanisms involved? We evaluate extant research by adapting the context-intervention-mechanism-output framework, and adopting a mechanism-based theory building approach for synthesising our findings. This study makes three contributions: first, we enrich epistemology by adopting a process view as we show that BMI is a series of interdependent mechanisms. Second, we identify six mechanisms unique to the phenomenon. Third, we offer a prescient outlook of BMI change as a metatheory. JEL Classifications: M10, O30, O31, O39