Abstract: Objective To understand the mental health literacy levels and their influencing factors among middle school students in Minhang District of Shanghai City, and to provide a basis for formulating mental health promotion strategies. Methods A multi-stage stratified cluster sampling method was adopted to select middle school students from 14 towns, streets, and industrial parks in the district from September to October 2023. A questionnaire survey was conducted, covering basic information and the Adolescent Mental Health Literacy Rating Scale. The scale included 22 items across four dimensions, namely knowledge, recognition ability, attitude, and behavior. Each item was scored using a 5-point Likert scale, with a maximum total score of 110 points. Reverse items were scored accordingly, and the total score was the sum of all item scores. Higher scores indicated higher levels of mental health literacy. A score of 88 points or above was considered as having mental health literacy. A multiple linear regression model was used to analyze the influencing factors of mental health literacy. Results The average mental health literacy score of the 3,963 middle school students in Minhang District of Shanghai City was (85.42 ± 11.27), with 45.22% of students having adequate mental health literacy. Univariate analysis showed that female students, junior high school students, and those without stressful events or physical illnesses in the past three months had higher total scores of mental health literacy. Statistically significant differences in total scores were also observed among students with different family economic statuses, parental education levels, frequency of physical exercise, parental relationships, father-child relationships, and mother-child relationships (all P<0.05). Multiple linear regression analyses showed that female students, those with better family economic conditions, higher maternal education levels, and harmonious mother-child relationships had higher mental health literacy scores. In contrast, high school students and those who participated in less physical activity had lower mental health literacy scores. Multivariate logistic regression analysis indicated that students who were female (OR = 1.340), had superior family economic status (OR = 2.000), had mothers with a university education (OR = 1.501), had lost one parent (OR = 2.189), or reported harmonious mother-child relationships (OR = 2.052) were more likely to meet the criteria for mental health literacy, whereas those who rarely engaged in physical exercise (OR = 0.502) were less likely to do so. Stratified analysis showed that mental health literacy levels among junior high school students were positively correlated with being female, having a mother with a university education, and having harmonious mother-child and father-child relationships, and negatively correlated with occasional or rare participation in physical exercise. Among senior high school students, mental health literacy levels were positively correlated with being female, having good or superior family economic status, having a mother with a university education or higher, and having a harmonious mother-child relationship. Conclusion The prevalence of adequate mental health literacy among middle school students in Minhang District of Shanghai City was approximately 45.22%. Gender, grade level, family economic status, maternal education level, physical activity participation, and mother-child relationship were independent factors associated with the level of mental health literacy among middle school students. Mother-child relationship and physical activity were potential intervention points. It is recommended to implement targeted health promotion for key groups, such as high school boys, students from economically disadvantaged families, and those with low levels of physical activity.