BACKGROUND: In many countries worldwide, heavy drinking can cause harm not only to drinkers but also to those around them. OBJECTIVE: To examine the prevalence and predictors of secondhand effects of alcohol use among students in Vietnam. DESIGN: In this cross-sectional study, a multistage sampling strategy was used to select 6,011 students (from the first to final study year) of 12 universities/faculties in four provinces in Vietnam. During class, students filled in a questionnaire asking for demographic information, and about alcohol-related problems and details of secondhand effects of alcohol during the past year. Exploratory factor analysis of the secondhand effects indicated two factors: non-bodily harm and bodily harm. A logistic regression model was used to explore the association between predictors and non-bodily harm and bodily harm. RESULTS: The prevalence of secondhand effects of alcohol is high among students in Vietnam: 77.5% had non-bodily effects and 34.2% had bodily effects. More than 37% of the population reported three to four non-bodily effects and more than 12% reported two to three bodily harms due to the drinking of others. However, most respondents who reported secondhand effects experienced these less than once per month. Factors most strongly associated with the yearly non-bodily harm were the weekly drinking habits of the people the respondents live with, and living in a smaller city; the factor most strongly associated with the yearly bodily harm was the respondent's own alcohol-related problems. Moreover, weekly drinking habits of the people the respondents live with, and respondent's own alcohol-related problems are strongly associated with the frequent experience of non-bodily and bodily effects of alcohol. CONCLUSIONS: In addition to dealing with alcohol-related harm of drinkers themselves, preventing secondhand effects should also be a major focus of prevention policy.