This chapter explores the historical development and theoretical underpinnings of Mindfulness-Based Stress Reduction (MBSR), tracing its journey from Buddhist monasteries to Western healthcare settings. It examines the pivotal role of Jon Kabat-Zinn in developing and popularising MBSR, and investigates the program’s theoretical framework, which integrates Buddhist concepts, psychological theories, and neuroscientific findings. The chapter discusses key psychological perspectives, including attention regulation, emotion regulation, and embodied cognition, while incorporating relevant neurobiological evidence. It also addresses criticisms of MBSR’s secularisation and explores the significance of understanding MBSR’s history and theoretical foundations for research, practice, and future developments. By providing a comprehensive overview of MBSR’s origins and mechanisms, this chapter offers valuable insights for researchers, practitioners, and those interested in the intersection of contemplative practices and modern healthcare.