The novel coronavirus infectious disease (COVID-19) pandemic has negatively impacted not only our physical health but also mental health, including increasing depressive and anxiety symptoms. In particular, socially and physically vulnerable populations, such as people experiencing homelessness (PEH), may be more likely to have their mental health worsened by the pandemic due to having more difficulty meeting basic human needs. Therefore, this study aims to assess the impact of COVID-19 on mental health of the homeless in Japan by evaluating depressive and anxiety symptoms and identifying the associated factors particularly, sociodemographic variables as age, employment status and the fear and perceived risk of COVID-19 infection. A cross-sectional interview survey among 158 PEH in Osaka Prefecture was conducted from April to May 2022. The survey included sociodemographic questions and history and perceived risk of infection with COVID-19. Depressive symptoms were measured using the nine-item Patient Health Questionnaire (PHQ-9) and anxiety symptoms using the seven-item Generalized Anxiety Disorder Scale (GAD-7), and the fear of COVID-19 using the seven-item Fear of New Coronavirus Scale (FCV-19S). In this study, the prevalence of depression (PHQ-9≥10) was 38.6%, anxiety disorder (GAD≥10) was 19.0%, and high fear of COVID-19 (FCV-19S≥19) was 28.5%. Univariate logistic regression analysis revealed that PEH in younger age groups (18-34 years), and with joblessness, higher perceived infection risk, and higher fear of COVID-19 were more likely to suffer from depression and anxiety (p<0.05). These results indicate that the younger PEHs with worsened economic conditions and therefore, feel threatened by COVID-19 the pandemic are at higher risk of mental health deterioration. More focused research and mental health services need to be provided to this population in the future.