Migration is often accompanied by significant shifts in nutrition and lifestyle behaviours, which may contribute to increased vulnerability to chronic diseases among migrant populations. This pilot study investigated the association between post-migration nutrition and lifestyle transitions and the risk of developing nutrition- and lifestyle-related chronic diseases among Nigerian migrants living in New South Wales (NSW), Australia. An online questionnaire, culturally adapted to the Nigerian context, was developed using Qualtrics and distributed through Nigerian community networks. The questionnaire comprised three sections: socio-demographic characteristics, nutrition and lifestyle behaviours before and after migration, and history of chronic diseases. A total of 97 Nigerian migrants participated in the study, with a mean age of 37.04 years (SD = 7.2); 50.5% were male and 49.5% female. Most participants (67%) migrated between 2013 and 2019, and the majority (68.7%) were married. In terms of income, 56.3% reported middle-income earnings ($A37,000–90,000), while 17.7% and 26.0% fell into minimum and high-income brackets respectively. Data analysis was performed using STATA version 16. Descriptive statistics were used to summarise demographic data, and inferential statistical techniques, including Chi-square, ANOVA, and multiple regression, were applied to explore associations between post-migration lifestyle changes and chronic disease outcomes. Results revealed substantial changes in dietary patterns following migration. Fruit and vegetable consumption significantly declined post-migration, while the intake of dairy products, fats, and processed foods increased. There were also notable reductions in the consumption of grain-based foods and seafood, alongside an increase in meat and alcohol intake. Physical activity levels dropped markedly after migration, with many participants reporting a shift towards more sedentary lifestyles. These changes were significantly associated with reports of lifestyle-related chronic conditions such as hypertension, osteoporosis, dental diseases and obesity. Participants who reported reduced physical activity and increased consumption of high-fat or processed foods were more likely to report having one or more chronic diseases. These findings underscore the health risks posed by acculturation-related lifestyle transitions among migrant populations. The study highlights the need for culturally appropriate health promotion strategies that prioritise healthy eating, active living, and chronic disease prevention within African migrant communities. Such strategies should be community-driven and supported by early screening and education campaigns. This pilot study provides preliminary but valuable evidence for understanding the nutritional and health impacts of migration on Nigerian Australians and lays the foundation for broader-scale research and policy development aimed at improving long-term health outcomes in African migrant populations across Australia.