This chapter provides an overview of some key occupational therapy concepts. It describes the occupational therapy process, an iterative sequence of finding out about a client, undertaking assessment, intervening and evaluation of outcomes. The chapter covers the four key occupational therapy models: The Person-Environment-Occupation model (PEO), The Canadian Model of Occupational Performance and Engagement (CMOP-E), The Model of Human Occupation (MOHO), and The Occupational Therapy Intervention Process model (OTIPM). The PEO model draws from environmental behaviour theories, theories of occupation and client-centred practice. CMOP-E model is grounded in the Canadian health, education and regulatory context and within its socio-culturally diverse population. MOHO proposes that inner capacities, motives and patterns of performance are maintained and changed through occupational engagement. The OTIPM is used in conjunction with client-centred, top-down, occupation-based approach to assessment and intervention. It aims to provide a structure to guide professional reasoning.