Background: The hospitalization of an infant within the complex environment of the Neonatal Intensive Care Unit (NICU) is incredibly stressful for families. Family-centered care (FCC) principles that integrate families into their parental role by forming relationships, sharing information, and supporting knowledge and skills are integral to NICU infant and parental health outcomes. Parents from a maternal-child health Parent Advisory Group in Alberta, Canada identified the need to evaluate parents’ experiences with FCC in the NICU. However, reliable tools developed with contribution from stakeholders to evaluate parent experiences are lacking, despite the importance of FCC in NICUs. Objective: This in-progress research responds to the parents’ call-to-action, with the objective to co-develop and validate an instrument to evaluate parents’ experiences with FCC in the NICU. The Neonatal Intensive Care Experience Reporting (NICER) Instrument is being co-developed by a team of five parents, three researchers, and three healthcare professionals. Methods: The NICER Instrument co-development includes four phases. Phase 1 (complete): defining NICU-specific FCC principles to underpin instrument co-development. Phase 2 (in-progress): selecting items and validating content with parent, researcher, and healthcare professional advisory groups. Phase 3: pilot-testing the instrument amongst 30 NICU parents. Phase 4: assessing instrument reliability and validity across 300 NICU parents. Results and Implications: This co-developed research highlights how healthcare system gaps can be identified by patients and families, and how solutions can be addressed by collaborative teams of knowledge users embedded within a healthcare system.  Throughout this research, the co-development team has gained practical knowledge to share related to (1) stakeholder engagement and network development; (2) working effectively with diverse knowledge users; and (3) the impact of patient and family input. Our takeaways from the co-development process highlight the importance of combining parent’s experience, researcher’s expertise, and healthcare professional’s knowledge to strengthen the content and relevance of FCC evaluation.