Objective: To investigate the associations of screen time (ST) and dietary behavior with sleep quality among first-year junior high school students, and further analyze the joint exposure effect of weekend ST and dietary usage, so as to provide scientific evidence for improving adolescent sleep quality and developing related health intervention measures. Methods: From September 19 to October 18, 2023, a combination of cluster sampling and convenience sampling method was used to select 733 first-year junior high school students from 4 public junior high schools in Jinshan District, Shanghai. ST on weekdays and weekends of students was investigated. The Chinese Diet Quality Questionnaire and the Pittsburgh Sleep Quality Index were applied to assess dietary behaviors and sleep quality. Binary Logistic regression was used to analyze the associations of ST and dietary behavior with sleep quality during weekdays and weekends. Results: The proportion of students with high level ST was 31.8% on weekdays and 65.3% on weekends. Students with poor dietary quality accounted for 45.3%, and the detection rate of poor sleep quality was 14.6 %. Binary Logistic regression analysis showed that, compared with students with low level ST on weekend and good dietary quality, those with high level ST on weekend and those with poor dietary quality had increased risks of poor sleep quality [ OR (95% CI )=1.89(1.10-3.26), 2.30(1.47-3.58), both P <0.05]. Combined exposure showed that compared to students with good diet quality and low level ST on weekend, students with good dietary quality and high level ST on weekend, those with poor dietary quality and low level ST on weekend, and those with poor dietary quality and high level ST on weekend also had increased risks of poor sleep quality [ OR (95% CI )=3.00(1.25-7.25), 4.07(1.60-10.33), 5.72(2.37-13.81), all P <0.05]. Conclusion Excessive weekend ST and poor dietary quality are associated with poor sleep quality among first-year junior high school students, and their co-occurrence further increases the risk.