This article contributes to an understanding of the nature of sustainability transformation experiments. We compare these experiments with classical experiments in the natural and social sciences along three central dimensions: 1) aims related to knowledge production, 2) roles of experimenters and participants, and 3) unpredictability of outcomes. We look at how experiments are understood in transition management and reflexive governance – two influential theories in current thinking about sustainability transformations that highlight the importance of experimentation. We shed light on implicit assumptions within experimentation for sustainability, especially regarding normativity, unintended outcomes and the roles of different actors. The analysis points towards a need to better understand experiments that directly deal with the (multi-level) governance set-up to enable sustainability transformations. Overall, we argue that being aware of the nature of experiments allows specifying experimental processes, distinguishing them from other types of learning, and helps develop strategies to apply experimentation in meaningful ways in sustainability transformations.