Serious games – games designed for purposes beyond recreation – rely on input from experts, stakeholders, and target audiences to ensure they meet their objectives in an accurate, authentic, and sensitive manner. These objectives may range from education to encouraging social change. Yet existing frameworks, while offering sound guidance on design principles and practices, are often unclear about how and when to involve key stakeholders, risking underutilising domain-specific experience and expertise. To address this gap, we propose an integrative design process for creating “seriously fun games” that applies an iterative, multi-stakeholder approach across three phases: Co-discovery, Co-design, and Co-evaluation. We illustrate the process through case studies (e.g. Built from Beneath, T Cell Titans) where sustained stakeholder engagement was critical in defining game purpose, shaping impactful narratives, aligning mechanics with objectives, and anticipating audience interpretations. This work contributes a replicable, stakeholder-driven methodology for designers seeking to create entertaining titles that support learning and address complex societal issues.