Hope lies at the core of human psyche. It has a unique power to propel individuals, groups, organizations, and communities to action and can sustain their energies to help them achieve their goals. Hope is differentially conceptualized and studied as an emotion; as a positive motivational state incorporating elements of pathways and agency thinking and also as goals pursuit cognitions that can cause emotions; and, lately, as a character strength. Thus, hope research and practice transverses major theoretical and applied fields of psychology (namely positive) developmental, educational, and counseling psychology. Long-established links between hope and well-being places it in a unique position to affect positive youth development through positive education practices but also to enhance physical and mental health and positive psychosocial adaptation throughout the life cycle with the use of successful approaches in therapy and counseling. Established criteria for hope-based interventions and programs were developed all over the world with the express dual aim to enhance well-being and reduce psychopathology in different populations, ranging from children, adolescents, youths, and adults with and without physical and mental health problems and learning disabilities; and also across various settings, as diverse as educational institutions, therapy and counseling, recreational centers, and correctional facilities. Overall, hope-based interventions were successful in enhancing positive psychosocial outcomes and reducing depression and other problems. Underlying mechanisms that drive hope programs include the development of upward spirals of positive emotions that help people build enduring psychosocial resources; the process of goal setting and pursuit in itself; and the identification of optimal combinations of individual characteristics and intervention goals and techniques. A wide range of individual factors, such as participants’ and implementers’ characteristics and levels of motivation, in addition to contextual factors such as protocols, research designs, techniques, materials, analyses, and reporting choices impact the effectiveness of hope interventions. Future research can benefit from targeted hope interventions, matching specific needs, skills, and capacities of people and groups in different settings, including educational, therapy, organizational, and community ones, which can greatly improve academic performance, physical and mental health, productivity, and life quality.