During the COVID-19 pandemic, undergraduates found themselves in an unprecedented social situation. Campuses across North America closed, as universities moved to remote learning. When in-person classes resumed, students had to negotiate the return to on-campus life. The current investigation examines predictive associations between pandemic-related stressors and distress during this transition, focusing on social media activity as a potential moderator. A longitudinal sample of 349 students at an urban university (116 men, 222 women, 11 nonbinary; Mage = 20.37) completed consecutive waves of measures (fall 2021 to spring 2022). A cross-sectional replication was recruited in spring 2022 (163 men, 229 women, 34 nonbinary). In both samples, we assessed social media activity using a newly developed measure. We also assessed internalizing symptoms, loneliness, and exposure to pandemic stressors. COVID-19 stress predicted increases in internalizing symptoms, but the effect held only for students who acknowledged high levels of active online communication.