Prevalent electronic cigarette (e-cigarette) use in schools may undermine tobacco denormalisation, and thus increase tobacco use in students. We investigated the associations of school-level e-cigarette use prevalence with student-level intention and behaviours related to e-cigarettes, cigarettes, and other tobacco products. In a 2014-15 school-based cross-sectional survey of 41035 secondary school students (grade 7-12; age 11-18 years) in Hong Kong, information was collected on the use of e-cigarettes, cigarettes, and non-cigarette tobacco products (NCTPs), susceptibility to e-cigarette and cigarette use, intention to quit cigarette smoking, and sociodemographic characteristics. The adjusted odds ratio (AOR) of e-cigarette use susceptibility in relation to high (vs low) school-level e-cigarette use prevalence was 1.40 (95% CI 1.05-1.87) in never e-cigarette users. The AORs of cigarette smoking susceptibility in relation to medium and high (vs low) school-level e-cigarette use prevalence were 1.24 (1.01-1.52) and 1.34 (1.02-1.75), respectively, in never cigarette smokers. School-level e-cigarette use prevalence was associated with ever and past 30-day cigarette smoking, but not with intention to quit (in past 30-day cigarette smokers) or past 30-day NCTP use. The findings highlight the importance of strictly banning e-cigarettes in schools, and add to the evidence that prevalent e-cigarette use in adolescents may increase cigarette smoking prevalence.