Several studies reported changes in sexual activities during the COVID-19 pandemic. However, there is a lack of comprehensive systematic reviews in this field. We aimed to systematically review the changes in sexual activities and risky sexual behaviors during the COVID-19 pandemic. This review adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist to improve transparency of our study. The results indicated a considerable decline in the frequency of sexual intercourse, particularly in singles and people with casual dating. Factors associated with sexual activity during the COVID-19 restrictions were depression, stress, lack of intimacy, inability to leave home, work schedule shifting, poor privacy, fear of COVID-19, lack of nightlife, and university educational level. Considering different groups of the population concerning their sexual behaviors is a necessary step in approaching healthy sexual behavior strategies, through which the adverse effects of a pandemic are minimized.