Introduction: Urbanisation in Indonesia has been associated with a transition in nutrition which has been, in part, marked by an increased purchasing of readyto-eat, energy-dense, nutrient-poor foods. Women are responsible for purchasing and preparing food for the family. Their purchasing behaviours differ in various environments and population groups. This qualitative study was undertaken to explore the food environmental factors that influenced food purchasing behaviour of women who were the household food gatekeepers. Methods: The study was conducted in a slum area in East Jakarta. Eighteen overweight-obese and nonobese women who fulfilled the study’s inclusion criteria were recruited for interviews that used a semi-structured questionnaire. Emic observations were conducted in order to identify typical food purchasing activities. The data were coded and categorised using qualitative data analysis and research software (Atlas.ti 7 for Windows). Results: Most of the women purchased ready-to-eat foods rather than cook at home, either for the family or their own consumption. Several food environmental factors influenced women’s purchasing behaviour, including time and cost efficiency, food availability, family, exposure to ready-to-eat foods and food store marketing strategies. These factors led to the consumption of unhealthy foods that were high in fat, carbohydrate, sugar and salt that some of which may cause obesity. Conclusion: Purchasing unhealthy food was observed to be strongly linked with food-related environmental factors. This study provides an understanding of women’s food purchasing behaviour and highlight potential ways to foster healthier purchasing behaviour among urban slum dwellers.