Even before the onset of the COVID-19 pandemic, researchers had raised concerns about the mental health of youth worldwide. One response has been the development of positive psychology interventions (PPIs) designed to enhance well-being. This study, conducted at a Thai university, investigated the impact of an online positive psychology course containing several PPIs on student well-being as measured by the EPOCH Measure of Adolescent Well-Being, the Satisfaction With Life Scale (SWLS), and Subjective Happiness Scale. The scores of the students in the positive psychology course (n = 84) increased in all areas measured, with statistically significant increases in the Perseverance, Optimism, and Happiness subscales of the EPOCH. Meanwhile, the scores of the control group (n = 105) decreased in all but two areas, with statistically significant decreases in the SWLS and Optimism. These findings suggest that teaching PPIs online can positively impact students' well-being.