Objective: We examined undergraduates' concerns about returning to campus and online learning from home. Participants: Undergraduates majoring in STEM (Science, Technology, Engineering, and Mathematics) at US universities/colleges. Methods: Participants completed an online survey in July 2020. We content-analyzed responses to open-ended questions about concerns about fall 2020. Results: Students (N = 64) were 52% women, 47% low socioeconomic status (SES), and 27% non-Hispanic white. Concerns about returning to campus included student noncompliance with university COVID-19 prevention guidelines (28%), infection risk (28%), poor instructional quality (26%), inadequate university plans for preventing/handling outbreaks (25%), negative impacts on social interactions (11%), and transportation/commuting (11%). Concerns about learning from home included difficulty focusing on schoolwork (58%), lack of hands-on/experiential learning (24%), negative impacts on social interactions (19%), family/home environment (15%), concerns that online learning wastes time/money (10%), and inadequate technology/Internet access (5%). Conclusions: Universities should address student concerns and provide resources to overcome barriers to effective learning.