Introduction: Poor eating behaviour is known to lead to nutritional deficiency among adolescents. At the same time, poor eating behaviour characterised by dietary excesses could lead to overweight and obesity. The present study aimed to explore the eating behaviour of adolescent schoolgirls in Malang, East Java Province, Indonesia, and to determine the factors that influenced their eating behaviour. Methods: This was a qualitative study, guided by the Social Cognitive Theory (SCT), which focused on individual and environmental influences to better understand health-related behaviours, such as eating behaviour. Triangulation was applied to the study subjects (adolescent girls, their mothers, and school staff). The methods used included individual in-depth interviews and focus group discussions. Qualitative data analyses were performed using Atlas.ti 7. Results: Most participants showed poor eating behaviour that was characterised by skipping breakfast, frequent consumption of fast foods and the consumption of local food with low nutrient content. Their eating behaviour was influenced by individual factors including personal preferences, the price of the food, and by environmental factors, such as the family, school and neighbourhood. Conclusion: Our findings showed that adolescent girls in Malang appeared to be aware of healthy eating but they showed unsatisfactory eating practices. Interventions are suggested to improve the poor eating behaviour of the adolescents toward avoiding malnutrition consequences.