Background and Aim: The ability to make sense of nutrition facts on food product labels is an essential skill for making informed food choices. These decisions are important especially in children and adolescents in light of growing concerns over food-related health issues, such as obesity, diabetes, and hypertension later in adulthood. Considering the important role of formal education system in improving food and nutrition literacy, the present study aimed to evaluate food label literacy among students in elementary and high schools in Iran. Also, the content of the text-books on both levels were analyzed to determine to what extent food label literacy has been addressed. Data were taken from a large study of Food and Nutrition Literacy (FNLIT) funded by the National Nutrition and Food Technology Research Institute (NNFTRI). Methods: This cross-sectional study was undertaken on 803, 5th and 6th grade elementary and 667, 12th grade high school students in Tehran city. Weight and height were measured and age- and sex-specific BMI z-score calculated. Food label literacy was measured by a sub-scale of a valid self-administered Food and Nutrition Literacy (FNLIT) questionnaire. Demographic and socio-economic characteristics were collected by a questionnaire through interviewing. Content of all elementary and high school textbooks (214 textbooks) were analyzed regarding food label in the educational year 2016- 2017. Logistic regression was used to assess the association between independent covariates with food label literacy. Results showed that a high proportion of primary and high school students had low level of food label literacy (76.0% and 45.4%, respectively). Logistic regression analysis adjusting for confounding factors such as demographic and socio-economic factors, showed that students with low food label literacy were more likely to be obese (OR=1.78, 95% CI=1.03-3.07). Among high school students, the probability of having low food label literacy in girls was higher than boys (OR= 1.963, CI= 1.38 – 2.79). The content analyses of elementary and high school textbooks showed that only one textbook (the science book of 6th grade in elementary school) had introduced food label and only with regard to energy calculation. Furthermore, it did not reflect the present labeling frame in Iran. In other words, food label literacy has not been considered in formal education textbooks.Conclusion: The results suggest the need for greater attention for improving food label information and skills as a key determinant of healthy food choices. Even though low food label literacy is less frequent in elementary students compare to adolescents this is not necessarily as a result of learning through education system and probably is due to their exposure and experience as they grow up. This will involve reevaluating the curriculum and text-books of schools, as well as the development of nutrition interventions via different media with regards to practical skills for food label literacy.