Collaborations between startups and established firms are changing how organizations innovate and bring new technologies to market, yet they remain difficult to initiate and sustain without the involvement of intermediaries. Drawing on an in-depth study of a national matchmaking program in Sweden, we show how intermediaries orchestrate these collaborations from first contact to scalable partnership. We offer a framework that spells out the actions intermediary managers should take throughout the collaboration process. We conclude by presenting three strategic questions and evidence-based practices to guide intermediaries in navigating corporate–startup relations, along with policy recommendations for creating the enabling conditions necessary to make these collaborations work at scale.