Successful startups are often launched and developed by teams. Scholars have investigated how these teams are put together, and revealed that emotions are likely to both emerge and influence outcomes as entrepreneurs collaborate. However, less is known about how team members interact to manage the uncertain and emotional processes of turning an idea into a profitable product or service. Employing a qualitative multiple case study, I ask: How do startup teams navigate uncertainty through coordination and affect (emotion) regulation? In doing so, this project aims to contribute to theory on small group dynamics and emotion regulation in entrepreneurship, as well as theory on emergent coordination and organizational learning more generally.