Homelessness is a relatively new phenomenon in Iran and has attracted public attention only in recent years. This article benefits from a so-called “pathway to homelessness” approach to study the relationship between drug abuse and social exclusion in Tehran. For the purpose of the study, 32 homeless men were interviewed. The whole process of investigation was organized utilizing grounded theory; categories were achieved using the constant comparison method. Three important risk factors for homelessness were identified and the connection between homelessness and different types of social exclusion experienced by the respondents was analyzed. At the end, Some suggestions has been made to improve the situation in the country.