This paper reports the mediation effect of gratitude on the influence of loneliness on life satisfaction among college students during the COVID-19 pandemic. A survey was conducted in April 2022 on 282 college students who live in K City, Republic of Korea, to measure loneliness, life satisfaction, and gratitude. We used structural equations to identify relationships among variables. Loneliness was negatively correlated with both life satisfaction and gratitude, but gratitude was positively correlated with life satisfaction. Gratitude partially mediated the effect of loneliness on life satisfaction. This result indicates that loneliness had a direct effect on life satisfaction, but the effect was affected by gratitude. Therefore, when considering the contextual factors due to the COVID-19 pandemic, college students' life satisfaction must be promoted, and positive psychological capital such as gratitude should be cultivated. This study contributes to understanding the mental health of college students who experienced the COVID-19 pandemic and to promoting this health by increasing each individual's life satisfaction.