This chapter examines how aging shapes the development and experience of person–environment misfit across the working lifespan. The authors propose a conceptual model linking age-related changes in individual abilities and needs with evolving environmental demands and supplies, leading to both objective and subjective misfit. Drawing on lifespan developmental theory, they explain how physiological, cognitive, emotional, and motivational shifts can create discrepancies between workers and their jobs, organisations, and social environments. The model distinguishes between short-term experiences of misfit and longer-term identity changes, showing how these processes affect occupational strain, well-being, job attitudes, and performance. Importantly, it highlights reciprocal effects: employees may proactively or adaptively respond to misfit through job crafting, learning, or re-evaluating their work goals. The chapter calls for longitudinal research to capture how misfit develops and resolves over time and identifies practical strategies for organisations to support older workers through job design, re-skilling, and inclusive HR practices. By integrating aging and misfit literatures, the chapter reframes misfit as a dynamic, developmental process and provides a foundation for understanding successful and unsuccessful ageing at work.