Abstract Objective To evaluate the prevalence of Internet addiction (IA) and its associated factors among students at an Educational Institution in Southern Brazil. Method This is a cross-sectional study, targeting a sample of students aged from 14 to 20 years. They were selected by random sampling to be representative of the 4038 students enrolled at the institute at the time. IA was assessed using the Internet Addiction Test (IAT). Screening for anxiety and/or depressive disorders was performed using the Well-Being Index (WHO-5). Results The prevalence of IA was 50.8% and the rate was higher among individuals who had screened positive for depressive or anxiety disorders than among those who had not (p = 0.003). There was an association between IA and access to certain types of content, such as gaming (p = 0.010), work and study related content (p = 0.030), and using the internet to access sexual content (p < 0.001). Conclusion Further studies are needed to confirm the high prevalence of IA and explore factors associated with it in samples with similar characteristics to ours. The associations between this dependency and positive screening for anxiety and/or depressive disorders and the types of content accessed are an alert to the existence of these important relationships and illustrate the importance of studying them further. Knowledge about these associations provides an opportunity to implement measures for prevention, such as psychoeducation, and to offer adequate treatment.