Design science in the entrepreneurship field holds the promise of developing relevant knowledge with scientific rigor. Yet despite the promise of this approach, the entrepreneurship field still lacks guidance on how to plan, conduct, and assess design science work. In order to develop theoretically grounded principles, we first make our perspective on design science explicit. We characterize design science in entrepreneurship as a specific scientific approach that shares the values of practice (i.e., usefulness) and uses the methods of science (i.e., scientific method plus more specific, scrutable methods). We conceptualize design knowledge as a body of scientific knowledge that comprises both design object knowledge (e.g., situated artifact, and design principles), and design evaluation knowledge (e.g., usefulness, and social worth). Drawing on these foundations, we provide guidance on (1) how to make design knowledge contributions explicit, (2) how to position design science work, (3) how to effectively utilize prior knowledge, and (4) how to use fitting methods in design science work. The article contributes by further developing the conceptual foundations of design science in entrepreneurship and providing guidance on how to conduct and assess design science work in the entrepreneurship field.