Background: This study aimed to estimate the prevalence of iron supplement consumption and its associated factors among high school students in Iran. Methods: A mixed-methods (quantitative-qualitative) study was conducted in Zahedan, southeast Iran, in 2015. The sample comprised 400 high school students from different areas of Zahedan who were randomly selected. A standard questionnaire and semi-structured interview were used to collect data in the quantitative and qualitative phases, respectively. The data were analysed using SPSS software with one-way ANOVA and Pearson’s chi square. Additionally, content analysis was used for the qualitative analysis. Results: In total, 38.2% of the students had not consumed iron supplements in the past 16 weeks, and students in third grade had the highest non-consumption rate (P=0.006). There was a significant positive relationship between iron tablet consumption and grade point average in the last year (P = 0.003). Digestive problems, influence of family and friends, students’ reluctance, and poor environmental situations were the most important factors related to students’ refusal to take tablets. Conclusions: Most students did not take or irregularly consumed iron supplements. Based on the digestive problems of the students, improving the taste and quality of iron tablets is recommended