Objective To investigate adolescents' diet-related behaviors and risk factors in Shanghai. Methods Questionnaires were performed to get the information of dietary behaviors. A total of 90 schools in Shanghai were selected by stratified clustering sampling methods. Two classes were randomly selected in every school. Results A total of 20 651 students were selected from 90 schools in 17 districts in Shanghai, in which male students were 49.5% and female students were 50.5%. The qualified respondent's questionnaires were 99.2%. The mean age of respondents was (14.95±1.95) years. ① Dietary habits: in the past 7 days, 54.4% of the students did not drink milk every day, 49.5% of the students did not eat fruits every day, 25.9% of the students did not eat vegetables every day, and 2.9% of the students did not eat breakfast. ② Overweight/obesity-related behaviors: 23.7% of the students drank carbonated beverage every day, 18.7% of the students ate dessert frequently, and 6.1% of the students ate western fast food more than 3 days in a week. ③ Weight control behaviors: in the past 30 days, 32.1% of the students reduced the amount of food and calorie intake, and ate low fat food to lose weight, 8.7% of the students did not eat staple food to lose weight, 2.6% of the students chose fasting for a long time, and 1.4% of the students took weight-loss pills. Adolescents' diet-related behaviors in Shanghai were related to gender, parental educational level and whether the student was a boarder. Conclusion Overall, adolescents' dietary habits in Shanghai are healthy. Gender differences are found in behaviors which can lead to overweight/obesity, suggesting that gender differences should be taken into consideration when an intervention is conducted in the future.