Objective: To examine the association of the physical fitness index (PFI) with the co-occurrence of overweight/obesity and depressive symptoms among secondary vocational school students, so as to provide a scientific basis for promoting their physical and mental health. Methods: From September to December 2024, a convenience sampling method was used to recruit 5 141 students from 16 secondary vocational schools across eight provincial level regions in China (Fujian, Chongqing, Guangdong, Guangxi, Hubei, Jiangxi, Shanghai, and Zhejiang) for on site physical fitness testing, height and weight measurements, and questionnaire surveys, and the PFI was calculated. The overweight and obesity status was determined based on the Screening for Overweight and Obesity among School age Children and Adolescents. A self designed questionnaire and the Patient Health Questionnaire-9 (PHQ-9) were used to collect survey data. Chi-square test and Logistic regression analysis were used to examine the associations of PFI levels with overweight/obesity, depressive symptoms and their co-occurrence. Results: The detection rates of overweight/obesity, depressive symptoms, and their co-occurrence were 21.1%, 22.2 %, and 5.0%, respectively. Significant age differences were observed in 50 m run, sit and reach, 20 s repeated straddling, 20 m shuttle run performance, and PFI ( F =7.34, 7.49, 3.70, 14.25, 3.85, all P <0.05). Logistic regression analysis showed that having a medium or low PFI was associated with an increased risk of overweight/obesity among secondary vocational school students ( OR =1.82, 2.60), whereas having a low PFI was associated with an increased risk of co-occurrence of overweight/obesity and depressive symptoms ( OR =2.03) (all P <0.01). After stratification by sex, having a medium or low PFI was associated with increased risks of overweight/obesity and their co-occurrence with depressive symptoms among boys (overweight/obesity： OR =1.95, 3.16；co-occurrence： OR =1.57, 2.34, all P <0.05). Conclusion Low PFI is associated with increased risks of overweight/obesity and co-occurrence among secondary vocational school students, and the association is more pronounced among boys.