Objectives: Household overcrowding (HC) can contribute to both physical and mental disorders among the members of overcrowded households. This study aimed to measure the status of HC and its main determinants across the provinces of Iran. Methods: Data from 39 864 households from the 2016 Iranian Household Income and Expenditures Survey were used in this study. The Equivalized Crowding Index (ECI) and HC index were applied to measure the overcrowding of households. Regression models were estimated to show the relationships between different variables and the ECI. Results: The overall, urban, and rural prevalence of HC was 8.2%, 6.3%, and 10.1%, respectively. The highest prevalence of HC was found in Sistan and Baluchestan Province (28.7%), while the lowest was found in Guilan Province (1.8%). The number of men in the household, rural residency, the average age of household members, yearly income, and the household wealth index were identified as the main determinants of the ECI and HC. Conclusions The study demonstrated that the ECI and HC were higher in regions near the borders of Iran than in other regions. Therefore, health promotion and empowerment strategies are required to avoid the negative consequences of HC, and screening programs are needed to identify at-risk families.