Background: Coronavirus disease 2019 (COVID-19) is a global public health emergency and may result in psychological problems such as anxiety and depression in general population. Therefore, this study aimed to determine the prevalence of anxiety and depression and their associated factors in general population of Iran during the COVID-19 pandemic.Methods: We conducted this web-based cross-sectional study on 5328 individuals in Iran, between 17 and 29 April 2020. Data were collected through an anonymous online questionnaire via social media like WhatsApp and Telegram. The online survey collected information on demographic characteristics, COVID-19-related variables, and anxiety and depression. Anxiety and depression were assessed using the Generalized Anxiety Disorder-7 (GAD-7) and the Patient Health Questionnaire-9 (PHQ-9), respectively. Simple and multiple logistic regression analyses were performed to determine independent predictors of anxiety and depression.Results: The mean GAD-7 and PHQ-9 total scores were 7.17 (SD=5.42) and 7.80 (SD=6.68), respectively. The prevalence of anxiety, depression, and comorbid anxiety-depression were 30.1%, 33.4%, and 22.1%, respectively. According to the adjusted analysis, anxiety was significantly associated with being female, being young and middle-aged, being unemployed or housewife, having chronic diseases, long time thinking about COVID-19, having family members, friends, and/or relatives infected with COVI-19, and death of family members, relatives or friends due to COVID-19. Same results were also found for depression. Furthermore, depression was associated with being single, being resident in urban area, and having high risk individual in family. Conclusion: The prevalence of anxiety and depression were considerably high in general population of Iran during the COVID-19 pandemic. In addition, the findings suggest that more attention needs to be paid to vulnerable groups such as women, young/middle-aged adults, unemployed people, people with chronic disease. Thus, a holistic approach, including management policies, psychosocial interventions, training, support, and tele-mental health, is absolutely crucial to reduce mental health problems of the COVID-19 and any outbreaks of other infectious diseases.