This paper seeks to demonstrate the utility of using two different approaches to sustainability system innovation in parallel, arguing that doing so provides valuable insights that would be lost if only one theoretical lens is used. The Multi-Level Perspective and Social Practice Theory have emerged as competing approaches for understanding the complexity of socio-technical change. The relationship between these two different camps can be on occasions antagonistic, but we argue here that that they are not mutually exclusive. Further, we suggest that their careful combination can in fact draw attention to critical points of intersection, where interaction between practices and regimes can either help or hinder processes of innovation. We illustrate this approach through two different cases of sustainability innovation and, whilst we caution against attempts at full theoretical synthesis, suggest that the intersection between systems of practice and socio-technical regimes is an important area of future research.