Background: As with countries worldwide, lockdown measures during the COVID-19 outbreak in Bangladesh were sudden and unexpected, and have the capacity to elicit serious psychological consequences. The present study examined the psychological consequences of COVID-19 in Bangladesh during the lockdown period. Methods: A nationwide online cross-sectional survey study recruited 10,067 individuals covering all 64 districts in Bangladesh via social media (April 1-10, 2020). The survey comprised questions concerning socio-demographics, knowledge of COVID-19, behavior towards COVID-19, fear of COVID-19, insomnia, depression, and suicidal ideation. Logistic regression and structural equation modeling (SEM) analyses were performed to identify the risk factors depression and suicidal ideation. Geographical information system (GIS)-based spatial analysis was used to identify district-wise susceptibility to depression and suicidal ideation. Findings: The prevalence rate of depression and suicidal ideation related to COVID-19 was 33% and 5%. Common risk factors for suicidal ideation and depression included being young, being female, being a cigarette smoker, having comorbid diseases, having high scores on the Fear COVID-19 Scale, and having insomnia symptoms. GIS-based maps detected high depression and suicidal ideation in the capital of Bangladesh and the districts near the capital as well as coastal areas where COVID-19 prevalence was high, as compared with districts with no reported cases. Interpretation: COVID-19 is associated with major psychological impact across Bangladesh, underlining the need of strategically located psychological support measures and improved access to mental health services, especially among women and younger people.Funding Statement: This study received no financial support from either government or non-government organizations.Declaration of Interests: The authors declare no completing interest to this work. Ethics Approval Statement: The ethical aspects were reviewed and approved by the Institute of Allergy and Clinical Immunology of Bangladesh ethics board, Bangladesh (IRBIACIB/CEC/03202005) and Biosafety, Biosecurity, and Ethical Committee of Jahangirnagar University, Bangladesh. Online informed consent was provided before survey participation.