This study explored the causes of drop-out from a community-based multi-component childhood obesity treatment intervention (MCTI), considering parent and child perspectives in order to develop future interventions which manage potential attrition more effectively. Semi-structured interviews explored attrition amongst a sample of children (n = 10) and their parents (n = 10) who dropped out of a community-based MCTI. Parents and children highlighted psychological and motivational issues (e.g. misaligned expectations, lack of desire to make behaviour changes and perceived costs of change outweigh the perceived gains) as the driving factor for their attrition alongside attitudinal, environmental, interpersonal and treatment variables. The complexity and interaction of factors associated with attrition identified in this study points to the challenges associated with reducing drop-out in MCTI’s. The views of families’ should be a key consideration in the design and implementation of treatment interventions to harness and sustain commitment to the treatment process.