Due to the repeated changes in the COVID-19 pandemic, we live in an era of various uncertainties that raise future anxiety and behavioral addiction problems. According to the Protection Motivation Theory (PMT), the present study attempted to explore the impact of COVID-19 intolerance of uncertainty (COVID-19 IU) on internet addiction (IA) among college students and the mediating role of future anxiety (FA) by constructing a mediating model. A questionnaire survey was conducted on 679 Chinese college students and PROCESS 3.5 was utilized to test the hypotheses. The results indicated that the COVID-19 IU was significantly positively correlated with IA and FA, and FA was significantly positively correlated with IA. COVID-19 IU had a significant positive predictive effect on IA; FA played a complementary partial mediating role between COVID-19 IU and IA. The results supported the PMT, which not only enriched our understanding of FA under uncertain life circumstances, but also deepened our understanding of the potential mechanisms of the effects of IA. Finally, discussions and suggestions were presented based on the results.