Background: Quality of diet is one of the most important factors in maintaining and improving the children's health; whereas, the quality of children's diet has not been studied in Isfahan City of Iran. This study was conducted to assess the adequacy of diet using healthy eating index (HEI)-2005 among 13-17 year-old students in Isfahan during 2014. Methods: The empirical data on dietary intakes were collected after three-days of food record. Later, a valid and reliable standard questionnaire was administered to measure the participants' physical activities. The participants' dietary intakes, daily energy, and nutrients were recorded by four researchers and were analyzed using SPSS 22by running ANOVA and Tukey tests. Results: The mean score of HEI in adolescents was 67.72. The correlation of calorie intake and mother's career with the HEI score was statistically significant (P < 0.05). Conclusion: Adults taking care of adolescents are recommended to improve the quality of diet among teenagers. They should also apply  relevant methods to correct the adolescents' nutritional habits.