This thesis aimed to develop an intervention to improve the life skills of British adolescent competitive sport participants, who are in full time education. Study one investigated the life skills needs of adolescent competitive sport participants and provided a participant-centred definition of life skills. The problem exists that it is unclear which life skills are needed by adolescent competitive sport participants and which life skills should be included in life skills programmes. As such, existing programmes may not reflect the needs of adolescents. The aim of this study was to examine the life skills needs of competitive adolescent sports participants from the perspective of youth sport participants, coaches, and experts in sport psychology and youth sport. Eighteen adolescent sports participants, fourteen coaches, and four experts in sport psychology and youth sport participated in a series of focus group interviews. An inductive analysis revealed how participants defined life skills and which life skills adolescent sports participants need. Life skills were defined as ranges of transferable skills needed for everyday life by everybody, that help people thrive above and beyond the normal requirements of everyday existence. Participants described the need for interpersonal skills including social skills, respect, leadership, family interactions, and communication. Personal skills including organisation, discipline, self-reliance, goal setting, managing performance outcomes, motivation, and identity were also reported. Participants described communication skills and organisation as the most important life skills for British adolescent competitive sport participants to acquire. Study two presents an in-depth, idiographic study illustrating how life skills were learnt through the experience of sport. The aim of the current study was to investigate how life skills could be learnt and improved through experiences in sport. (Continues...).