Citizen science (CS) is promoted as a useful practice for the achievement of the Sustainable Development Goals (SDGs). In this contribution we explore how CS aligns to the SDGs overarching pledge to ‘Leave no one behind’. We propose a framework to evaluate exclusionary processes in CS. We interlink three dimensions of CS inspired by existing CS typologies with five factors underpinning exclusionary processes. With this, we are able to situate existing literature on various exclusionary effects in CS within a structured framework. We hope this contribution sparks a discussion and inspires practitioners’ reflections on a more inclusive practice in CS.