Background: The outbreak of the COVID-19 pandemic in 2020 and its associated measures led to high levels of mental distress in the general population . Previous research indicated that young people are especially vulnerable for a wide range of mental health problems during the pandemic, but little is known about the mechanisms . This study examined mental distress and its contributing factors among young Belgian people.Methods: An online survey was widely distributed in Belgium during the first wave of COVID-19 in March, and 16–25-year-olds were selected as a subsample . Mental distress was assessed using the 12-item General Health Questionnaire (GHQ-12), and a threshold of ≥4 was used to discriminate mental distress cases from non-cases . Bivariate and multivariable logistic regression analyses were performed to evaluate possible predictors of mental distress, including demographics, chronic condition, history of mental health problems, social support, exposure to COVID-19, and several changes in everyday activities.Results: A total of 2,008 respondents were included, of which the majority was female (78.09 %) and student (66.82 %). The results indicate that about two thirds (65.49 %) experienced mental distress . In the multivariable regression model, significant (p <0.01) predictors of mental distress were female gender (OR = 1.78), low social support (OR = 2.17), loneliness (OR = 5.17), a small (OR = 1.63), or large (OR = 3.08) increase in social media use, a small (OR = 1.63) or large (OR = 2.17) decrease in going out for drinks or food, and a decrease in doing home activities (OR = 2.72) .Conclusion: Young people experience high levels of mental distress during the COVID-19 pandemic . Our findings indicate that mental distress was highest among women, those experiencing loneliness or low social support and those whose usual everyday life is most affected . The psychological needs of young people, such as the need for peer interaction, should be more recognized and supported.