The urban lab is an experimental governance approach for the co-creation of innovative solutions to urban challenges, such as climate change. However, urban lab scholarship has overlooked lab formation as a distinct process and is almost exclusively based on European cases. Therefore, little is known about the role of context conditions for lab formation in general and beyond Europe in particular. To address these gaps, this paper inductively analyses urban lab formation in five cities in Argentina, Brazil and Mexico, develops a framework for the comparative analysis of lab formation challenges, and asks: What do the challenges encountered and the solutions developed during lab formation in these cities tell us about the context dependence of the urban lab approach and what are the implications for its potential beyond Europe? Comparing insights from Europe to the findings from Latin America, the paper answers these questions and identifies future research questions.