In the enterprise software industry, large platform vendors have established partner networks with smaller providers of complementary solutions. This study takes the perspective of these complementors. How do they coordinate their partnerships with platform vendors? What are the circumstances under which different coordination mechanisms lead to partnership success? Based on existing theories and the findings from extensive qualitative research, a new explanatory model is developed. The study contributes to theory building efforts in the Information Systems discipline as well as in adjacent fields by providing a better understanding of partnership coordination and success. The implications for successful partnership management are highly relevant for practitioners.