Both drug use and sex work considered as serious health and social problems. This study aimed to find the relation between them in young Iranian women. A mixed method of data collection applied from 300 young female sex workers in Tehran and 39 in-depth interviews with key informants. Result show that 84.4 % of participants used drugs before sex work. 46.2% of their fathers and 56.6% of their husbands used drug. 13.6% of these women mothers were sex workers. Evidences stated that priority of drug addiction to sex work cannot be generally determined. This study finding indicated that young women use drugs mostly before sex work; but substance abuse after starting sex work was to reduce the mental and physical sufferings to facilitate working through raising sexual potency and to sink in ecstasy and ignorance meanwhile in most cases to be able to obtain drugs. Manuscript profile