While cross‐sector collaborations can create effective governance mechanisms for multi‐sectoral issues, little attention has been paid to how these arrangements operate in low‐ and middle‐income countries (LMICs), where state capacity is weak and the international donor sector is influential. A case study of the Scaling Up Nutrition (SUN) collaborative governance platform in Senegal is presented to explore how tensions between actors can be managed and how power is exercised through metagovernance. Through in‐depth interviews with policy actors (N = 30), network mapping of ties and activities among actors and document review, the study identifies challenges and opportunities for multi‐sectoral nutrition governance. The study identifies several challenges specific to scaling up multi‐sectoral policies including the relative power of non‐state actors, duplication of efforts and a lack of incentives for multisectoral collaboration across different sectors within government. The article concludes that to ensure democratic governance, government must be capable of metagovernance.