en Health Health Original Research Original Research <strong>Background: </strong>Health service utilization (HSU) is a significant health and political issue. Awareness of factors that affect HSU and the status of health service utilization can help health professionals improve their services. The aim of this study was to investigate the status of HSU and identify the factors affecting health service utilization among households residing in Tehran.<br> &nbsp;&nbsp; <strong>Methods:</strong> The present cross-sectional study included 1200 residing households from different regions of Tehran, the capital of Iran. They were selected by a multi-stage cluster sampling method in accordance with the zoning of Tehran concerning socio-economic development. Interviews were conducted by trained individuals using a health service utilization questionnaire introduced by the World Health Organization, Zimet&rsquo;s social support questionnaire, and demographic checklist during winter 2018 and spring 2019. Simple and multiple logistic regression models were applied to analyze the data. In order to include the factors related to the status of outpatient health service utilization, a set of bivariate analyses was conducted, and then the factors with a p-value of &le;0.20 were included in the multiple models. Data were analyzed using Stata 12 software.<br> &nbsp;&nbsp; <strong>Results: </strong>The results of the study indicated that the rate of outpatient HSU among households residing in Tehran was 63.61% (CI:60, 66.80). In addition, regarding the results of the study, asset index of family (OR=0.51, 95% CI: 0.28, 0.91), the level of awareness and knowledge of family members regarding health issues (OR=0.55, 95% CI: 0.34, 0.88) as well as the mother knowledge&nbsp; on health issues (OR=0.64 , 95% CI: 0.45, 0.93), the level of social support (OR = 0.50, 95% CI: 0.37,0.68), family health expenditure (OR=1.20, 95% CI: 1.18, 4.06), having a member with a&nbsp; sort of disability in family (OR=1.66, 95% CI: 1.01, 2.77), and having an alcoholic member in family (OR=2.44, 95% CI: 1.27, 4.68) were factors associated with outpatient HSU among households. Considering the adjusted values of odds ratios, the prevalence of the HSU varied according to the area of residence. It should be noted that the variables included in the model explained 15% of the changes in the prevalence of HSU.<br> <strong>&nbsp;&nbsp; Conclusion:</strong> According to the results of the study and in order to increase HSU in different classes, the level of social support, especially among women in the family due to their role in the general health of family members, should be enhanced. Also, policies should be adopted to increase the awareness, knowledge, and information of family members about health issues, lifestyle changes, nutrition, and health behaviors through social media.<br> &nbsp;<br> <gdiv></gdiv><gdiv></gdiv><gdiv></gdiv><gdiv></gdiv> Outpatient, Health service utilization, Household, Tehran 554 562 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-2646-1&slc_lang=en&sid=1 Neda SoleimanvandiAzar nedasoleiman@yahoo.com 200319475328460063179 200319475328460063179 No Department of Social Welfare Management, University of Social Welfare and Rehabilitation Sciences, & Preventive Medicine and Public Health Research Center, Psychosocial Health Research Institute, Iran University of Medical Sciences, Tehran, Iran Seyed Hossein Mohaqeqi Kamal hosseinmohaqeq@gmail.com 200319475328460063180 200319475328460063180 No Social Welfare Management Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Homeira Sajjadi safaneh_s@yahoo.com 200319475328460063181 200319475328460063181 No Social Welfare Management Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Hossein Malekafzali Ardakani malekafzali@sina.tums.ac.ir 200319475328460063182 200319475328460063182 No Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Ameneh Setareh Forouzan asforouzan@gmail.com 200319475328460063183 200319475328460063183 No Social Welfare Management Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran Salah Eddin Karimi Salahkarimi2009@gmail.com 200319475328460063184 200319475328460063184 No Social Determinants of Health Research Center, Health Management and Safety Promotion Research Institute, Tabriz University of Medical Sciences, Tabriz, Iran Gholamreza Ghaedamini Harouni Qaedamini@gmail.com 200319475328460063185 200319475328460063185 Yes Social Welfare Management Research Center, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran