As digital transformation accelerates, cybersecurity has emerged as a critical concern for organizations worldwide, driven by escalating cyber threats, geopolitical tensions, and increasingly complex supply chains. Effective inter-organizational collaboration in cybersecurity governance relies on trust, which influences information sharing, coordinated threat responses, and risk-management. This study explores how formal and informal rules shape trust dynamics in inter-organizational cybersecurity governance, using Ostrom’s Institutional Analysis and Development (IAD) framework. A grounded theory approach is employed through a systematic literature review and semi-structured interviews. Preliminary findings highlight key barriers to trust-building, including partnership failures, disinformation, and geopolitical trust deficits, while identifying potential solutions such as blockchain, AI-driven security models, and structured cybersecurity disclosure frameworks. Trust also requires governance frameworks that balance compliance with collaboration. By advancing theoretical and practical insights, this research informs policymakers, cybersecurity leaders, and IS scholars on designing trust-centric cybersecurity ecosystems in an era of global digital uncertainty.