This preliminary study examined the relationship between leisure time physical activity (LTPA) and psychosocial well-being in 53 adolescents who were previously diagnosed with cancer. Participants completed a mailed, self-administered questionnaire in which they recalled their LTPA (including leisure time exercise and organized sport) at three time points (prediagnosis, treatment, and posttreatment). They also reported their current psychosocial well-being by using measures of depression and self-concept. Examination of the LTPA data revealed four main patterns across the cancer experience that were labeled maintainers (active at all three time points), temporary relapsers (active prediagnosis, inactive during treatment, active posttreatment), permanent relapsers (active prediagnosis, inactive during treatment, inactive posttreatment), and nonparticipants (inactive at all three time points). Multivariate analyses of variance indicated that self-concept differed significantly across the four organized sport patterns. Follow-up univariate analyses revealed significant differences for general self-concept, physical abilities, parental relations, same sex relations, and opposite sex relations with effect sizes ranging from medium-large to large. Post hoc tests generally showed that the maintainers exhibited superior scores on psychosocial well-being compared with the other three patterns. It was concluded that LTPA patterns across the cancer experience may be related to psychosocial well-being in adolescents after cancer diagnosis but that further research is warranted.