Background Ethnic disparities in childhood overweight in the UK, and the cultural and contextual basis of disparities, are not well understood. The aims of this research were to identify patterns in childhood overweight across ethnic groups; explore child and parental perspectives and experiences that may contribute; and consider the implications for service design. Methods A mixed methods approach was utilised as follows: 1) a systematic review of the factors associated with adiposity in children from minority ethnic groups; 2) multilevel analysis of child measurement data for primary school children; 3) qualitative draw, write and tell interviews with an ethnically diverse sample of children aged 9-10 years; and 4) qualitative focus groups with parents from selected ethnic groups. Mixed methods analytical integration was performed using a joint display, following a thread and triangulation. Results Study 1 highlighted the lack of existing evidence to understand the basis of ethnic group disparities in childhood adiposity. Study 2 (n = 56, 409) found age and sex -related patterns of ethnic disparities in childhood overweight and obesity, indicating that children from Black African and Caribbean and Bangladeshi backgrounds had significantly higher odds at age 4-5 years vs White British. The same pattern was found for girls aged 10-11 years, whilst boys from South Asian, Black African, White Other and Mixed ethnic groups had significantly higher odds at this age. Study 3 (n=26) revealed that children viewed health as a choice, however ethnic group-specific experiences were not strongly apparent. Study 4 (n=35) identified universal and ethnic group-specific features of parents' lives influencing weight, emphasising the importance of cultural-contextual interactions upon family health behaviours. Mixed methods analytical integration allowed for a more complete appraisal of methods and understanding of the research issue. Conclusions The findings provide a detailed understanding of the cultural and contextual basis of ethnic disparities in childhood overweight, upon which to direct the planning of public health services.