Crowdsourcing has attracted increasing attention as an open innovation tool that enables firms to access the ideas and solutions of external crowds of participants. Among various crowdsourcing formats, hackathons have emerged as a form of collaborative crowdsourcing that emphasizes team-based collaboration among participants to co-create solutions to firms’ challenges under intense time pressures. Despite their increasing popularity, limited focus has been placed on understanding how hackathons should be organized and managed and the challenges that these time-intense collaborative events generate for both firms and participants. Based on a qualitative, multiple case study of six on-site hackathons, we identify and discuss four key design practices that shape these collaborative crowdsourcing forms, namely 1) problem formulation; 2) participant attraction and team composition; 3) developing the evaluation system; and 4) facilitating idea development. We show that these design practices are interrelated, with decisions about one design practice having important implications for the others, and discuss key challenges that arise from their combination. Overall, our findings highlight how organizing and managing hackathons is a complex matter that requires firms to adopt a more holistic and complementary approach. Implications for innovation management research and practice are discussed.