OBJECTIVE: The aim of this study was to investigate the relationship between nutritional self-efficacy, nutritional attitudeand behaviour of students with overweight and obesity. MATERIAL AND METHODS: This study was carried out with 192 students in 5th, 6th and 7th grades whose body mass index percentile value was over 85. The data were obtained with personal information form, dietary self-efficacy scale, nutrition attitude scale and dietary behaviour scale in this study. RESULTS: The nutritional self-efficacy mean score of the students was 5.58 ± 5.07, the nutritional attitude was 12.72 ± 2.52, and the nutritional behaviour mean score was 2.92 ± 6.03. There was no significant difference found between scale scores according to gender and body mass index classification, and students without an overweight family member had a more positive nutritional attitude. A positive relationship was found between nutritional self-efficacy and nutritional attitude and nutritional behaviour. CONCLUSIONS: Nutritional self-efficacy, nutritional attitudes and nutritional behaviour levels of children with overweight and obesity were found to be above the moderate level. Factors such as fast food eating habits and time spent with technological devices such as computers and TV, which increase the susceptibility to overweight and obesity, are effective in the levels of nutritional self-efficacy, nutritional attitude and nutritional behaviour.