Objective: The COVID-19 pandemic has adversely impacted mental health, with mood disorder patients at increased risk due to stress, isolation, and healthcare disruptions. While studies highlight rising depression and anxiety in these populations, comparisons of pre- and post-pandemic symptoms remain limited. This study examines the late-phase mental health effects of the pandemic on mood disorder patients and associated factors. Method: In our study, 67 patients diagnosed with mood disorders who were hospitalized between March 2019 and March 2020 were evaluated in the ninth month of the pandemic. Data were collected through face-to-face or online interviews, and clinical information such as sociodemographic characteristics, illness severity, and fear of COVID-19 was recorded. Results: Participants were 65.7% female and 34.3% male, with a mean age of 45.8+/-19 years. Of the patients, 32.9% had completed higher education, and 56.2% were unemployed. Interviews were face-to-face (44.8%) or telepsychiatric (53.7%). The mean pre-pandemic hospitalization duration was 41.6+/-24.8 days. No significant differences were found in HAM-D scores pre- and post-pandemic for major depressive or bipolar depressive patients. However, 55.2% had HAM-D >=8 during the pandemic. Patients with a history of COVID-19 infection showed significantly higher depression severity. Discussion: By the ninth pandemic month, over half of mood disorder patients had depressive symptoms. COVID-19 infection, lack of knowledge, and unmet psychological support needs were linked to depression. Restricted access to mental health services further increased depression rates. These findings highlight the psychosocial and biological impacts of the pandemic on mood disorders.