The prevalence of overweight/obesity is high among Black women in England, who also face high risks of pregnancy and childbirth complications. This study explored African migrant women’s perceptions of pre- and post-migration influences on their weight-related behaviours and weight management support during pregnancy. Interviews were conducted with women of child-bearing age from Ghana, Nigeria, and Cameroon (n = 23). Data were analysed using thematic analysis. Four themes were identified: changing dietary behaviours after migration, changing physical activity (PA) behaviours after migration, increased discourse on obesity, and weight management advice and support received. Navigating a new food environment, interactions with other populations in England, and the need to socialise influenced changes in dietary behaviours. Participants considered that living in England ‘makes you lazy’ due to its obesogenic environment, while increased discourses on obesity heightened weight awareness. Women struggled to relate to dietary advice from midwives but found PA advice useful. Relatives provided valuable support but could influence unhealthy weight-related practices. There is a need for interventions addressing gaps in weight management support for these women, especially considering their migrant backgrounds and multicultural identities. Further research is needed to understand their unique challenges, and collaborations with relatives could inform the development of effective weight management interventions.