College students are at high risk of problematic internet use (PIU). A great amount of research has focused on the PIU among college students. However, little is known about the change pattern of PIU across the college years. Moreover, how peer internet overuse behavior and peer attitude toward internet overuse work together to shape college students' PIU trajectory, and whether such peer contagion effects are equal for all students remain unclear. The present study used latent growth curve model to examine these issues. A total of 2572 Chinese college students (Mage = 18.37, SD = 0.85; 65% girls) participated in the study. They completed questionnaires regarding demographics, peer internet overuse behavior, peer attitude toward internet overuse, and friendship satisfaction at Wave 1, and PIU at Waves 1-4. After controlling for covariates, the findings revealed that (a) PIU slightly increased before the second year of college and then declined rapidly; (b) both peer internet overuse behavior and peer attitude toward internet overuse were related to the PIU at baseline; however, only peer internet overuse behavior was associated with the change of PIU; and (c) the effect of peer internet overuse behavior on PIU change was moderated by friendship satisfaction and gender. These findings emphasized the dynamic and context-sensitive nature of PIU and clarified how peer contagion unfolded with peer internet overuse behavior and peer attitude toward internet overuse. Theoretical implications and application of these findings are discussed. Copyright © 2020 The Foundation for Professionals in Services for Adolescents. Published by Elsevier Ltd. All rights reserved.