•Bangladesh has almost no country-representative researches addressing COVID-19 related mental health problems•5.0% suicidal ideation and 33.3% depression was reported from this nationwide study•The risk factors for both depression and suicidal ideation included - younger age, female, smoker, comorbidities and insomnia•Other COVID-19 related risk factors were its’ poor knowledge and greater fear, and not engaging in its preventive behaviors•GIS mapping presented district-wise distributions of depression and suicidal ideation. As with other 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. 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. 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. Self-reported scales and cross-sectional design of the study. 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.