Objective: To examine whether a remote, online, group-based mindfulness intervention results in effects during the COVID-19 pandemic. Participants: 111 college students: 58 in the intervention group, 53 in a waitlist control group. Methods: Randomized control trial (RCT) using a 4-week Koru Mindfulness program, investigating pre-to-posttest changes in the intervention group compared to time-yoked control participants. Results: Average effect size for all 21 variables measured was 0.48. The intervention produced significant benefits for mindfulness, rumination, worry, mood, stress, anxiety, three out of six aspects of psychological wellbeing (Autonomy, Environmental mastery, Self-acceptance) and physical activity. No significant effect was noted for depression (d = 0.33) or sleep (d = -0.13), and three aspects of psychological wellbeing (Personal growth, Positive relationships, Purpose in life). Conclusions: A remote, online, group-based mindfulness program yielded benefits on stress, anxiety, and mood in college students, even under the dire circumstances of a pandemic.