Background As electronic cigarettes (e-cigarettes) are becoming increasingly prevalent, adolescents are experiencing growing levels of environmental exposure to them. Investigating the status and influencing factors of such exposure is essential to inform the development of targeted tobacco control strategies for youth. Objective To investigate the environmental exposure to electronic cigarettes among vocational school students in Shanghai, identify its influencing factors, and assess its impact on e-cigarette use behavior. Methods By cluster sampling, a total of 4890 students were recruited from 4 vocational schools in Shanghai. A questionnaire was designed to collect information on general characteristics, tobacco use (cigarettes and e-cigarettes), peer/parental e-cigarette use, and environmental e-cigarette exposure (environmental aerosol exposure, e-cigarette sales exposure and e-cigarette-related information exposure). Data were collected via Wenjuanxing (an online survey platform) anonymously and analyzed using SPSS 24.0. Chi-square test and logistic regressionwere used to analyze the data. Results The current vaping rate and vaping attempt rate were 2.29% and 8.94% among all participants. The proportions of students exposed to e-cigarette aerosol, e-cigarette sales, and e-cigarette-related information were 41.0%, 63.3%, and 77.3%, respectively. The exposure to environmental e-cigarette aerosol was higher among male students (45.3%) than among female students (34.5%), while the exposure to e-cigarette sales (65.4%) and e-cigarette-related information (78.8%) were higher among female students than among males (61.9%, 76.2%), respectively (P<0.05). Having friends using e-cigarettes increased the risk of exposure to e-cigarette aerosol (OR=7.32, 95%CI: 6.37, 8.41), exposure to e-cigarette sales (OR=3.10, 95%CI: 2.70, 3.56), and exposure to e-cigarette-related information (OR=1.45, 95%CI: 1.25, 1.69). Current cigarette smoking, parental e-cigarette use, and not living on campus also increased the risk of environmental e-cigarette aerosol exposure and sales exposure among the participants (P<0.01). Higher pocket money was significantly associated with increased risks of exposure to e-cigarette sales and e-cigarette information (P<0.001). Environmental e-cigarette aerosol exposure increased the risk of current (OR=6.21, 95%CI: 3.75, 10.29) and attempt (OR=2.25, 95%CI: 1.82, 2.77) e-cigarette use among the participants. Furthermore, reporting exposure to two or more categories of e-cigarette sales and information was associated with a higher risk of e-cigarette use than those reporting no exposure (P<0.05). Conclusion The adolescents are severely exposed to environmental e- cigarette, which increases their risk of e-cigarette use. We recommend implementing measures to mitigate environmental exposures, strengthen tobacco control education, and reduce peer influence related to e-cigarette use, with particular attention to female adolescents and those with higher pocket money.