Objective: To compare physical activity (PA), sitting time, and substance use pre-COVID-19 and during COVID-19 pandemic among US college students. Participants: 484 students from a large Western university (20.6 ± 1.4 years, 80.0% female) were recruited. Methods: Self-reported online surveys were completed in June-August 2020. T-tests and non-parametric analyses were conducted for continuous and ordinal variables respectively. Results: Vigorous PA, moderate PA, and light PA decreased significantly by 32%, 27%, and 21% and sitting time increased significantly by 49% from pre-COVID-19 to during COVID-19 pandemic. Wine consumption was less during COVID-19 than pre-COVID-19 among female, non-first-generation, and White students. Sleep aids use was more frequent during COVID-19 than pre-COVID-19 pandemic among non-first-generation and White students. Conclusion: COVID-19 pandemic may influence college students' health behaviors including physical activity patterns, sitting time, and substance use. Effective health promotion and coping strategies should be widely available to college students during times of change and uncertainty.