Abstract Background: Feelings of isolation, insecurity, and instability triggered by COVID 19 could have a long-term impact on the mental health status of individuals. This study examined the prevalence and factors associated with the mental health symptoms of anxiety, depression, and stress during the COVID 19 pandemic in Bangladesh. Methods: From 1st to 30th April 2020, we used a validated self-administered questionnaire to conduct a cross sectional study on 10,609 participants through an online survey platform. We assessed mental health status using the Depression, Anxiety, and Stress Scale (DASS-21). The total depression, anxiety, and stress subscale scores were divided into normal, mild, moderate, severe, and multinomial logistic regression was used to examine associated factors. Results: The prevalence of depressive symptoms was 15%, 34%, and 15% for mild, moderate, and severe depressive symptoms, respectively. The prevalence of anxiety symptoms was 59% for severe anxiety symptoms, 14% for moderate anxiety symptoms, and 14% for mild anxiety symptoms while, the prevalence for stress levels were 16% for severe stress level, 22% for moderate stress level and 13% for mild stress level. Multivariate analyses revealed that the most consistent factors associated with mild, moderate, and severe of the three mental health subscales (depression, anxiety, and stress) were respondents who lived in Dhaka and Rangpur division, females, those who self quarantined in the previous 7 days before the survey and those respondents who experienced chills, breathing difficulty, dizziness, and sore throat. Conclusion: Our results showed that about 64%, 87%, and 61% experienced depressive symptoms, anxiety symptoms, and levels of stress, respectively. In Bangladesh, there is a need for better mental health support for females especially those that lived in Dhaka and Rangpur division and experienced chills, breathing difficulty, dizziness, and sore throat during COVID 19 and other future pandemics.