This dissertation aims at analyzing mindfulness as a concept and a multidimensional phenomenon in its historic and primordial but also contemporary contexts. In the course of examining this more general question, this dissertation targets four specific objectives: 1) classifying existing definitions of mindfulness, 2) critically analyzing and interpreting the Buddhist and Western interpretations and practices of mindfulness, 3) elaborating on the social and existential dimensions of mindfulness, and 4) applying these dimensions in advancing the notion of mindful sustainable aging in the context of successful aging. Paper I examines and assesses the numerous definitions of mindfulness that have been presented over the years by a wide range of scholars from a variety of disciplines. Paper II traces the roots of modern mindfulness in Buddhism. It continues by exploring the utility and practices of mindfulness in the context of social work. The definitions provided in Paper I and the Buddhist underpinnings discussed in Paper II call attention to the fact that in addition to the more commonly considered physical and mental dimensions, mindfulness contains a social and an existential dimension as well – dimensions that remain under-researched and not well understood. To redress this imbalance, Paper III elaborates on these two latter dimensions, emphasizing their potential to enhance health, wellbeing and meaning in life. Paper III further argues that a more nuanced understanding of physical, mental, social and existential mindfulness can be obtained by examining the interconnectedness of all four fields. Paper IV continues the discussion of the social and the existential dimensions of mindfulness with specific emphasis on their utility for successful aging, and advances the notion of mindful sustainable aging. Paper IV highlights the potential of mindfulness for living a meaningful life and boosting the elderly’s capacity to find deeper meaning in their final stage of life.