Background: Food preferences determine food choices, which are significantly associated with overweight/obesity and health outcomes worldwide. Obesity and overweight is one of the health problems of adolescents in the world. This study aimed at determining the relationship between food preferences, body mass index (BMI), and demographic variables among second-year primary school students of Malekan City, located in East Azerbaijan Province, Iran, during 2022 to 2023.  Methods: This cross-sectional and descriptive-analytical study was conducted on 582 male and female primary school students in the second grade in both public and private schools of the three towns of Malekan City (Malekan, Lilan, and Mubarakshahr) with a two-stage random cluster sampling method. A two-part online questionnaire including questions on background information and a researcher-made checklist of food preferences was used to collect data. Content validity ratio (CVR), content validity index (CVI), and Cronbach's alpha were used to check the validity and reliability of the questionnaire, respectively (CVI = 0.98, CVR = 0.91). Data were analyzed using Mann-Whitney test, t-test, one-way analysis of variance (ANOVA), Kruskal-Wallis test, and chi-square test at a significance level of 0.05 using SPSS software.  Findings: There was a significant association between food preference and sex (P < 0.001), age (P = 0.027), educational grade (P = 0.027), mother’s education (P = 0.028), mother’s job (P = 0.002), father’s education (P = 0.046), residence (P = 0.001), and family income (P = 0.002). There was a significant relationship between BMI with school type (P = 0.002), father’s education (P = 0.033), and mother’s age (P = 0.013).  Conclusion: The results of this study indicate the relationship between food preferences, BMI, and demographic variables of adolescents. Paying attention to the potential strategies to strengthen healthy eating patterns of adolescents and providing an educational program that can improve children’s eating behavior and reduce the possible burden of diseases related to eating behavior such as obesity on the country's health care system seem necessary.