Female sex workers are a deprived part of Islamic communities. It is necessary for public health policy makers to have knowledge about their mental health status. This study aims to have an evaluation of mental health among female sex workers in Tabriz for the first time in northwest of Iran. In this cross-sectional study, 48 female sex workers who had accepted to be evaluated were included. Sociodemographic and general mental health statuses, using General Health Questionnaire (GHQ-28), were recorded. Those with GHQ-28 score more than 23/24 in the first session were thoroughly interviewed in a second session in order to find out their specific mental disorder, using Structured Clinical Interview for DSM-IV axis 1 and 2 Disorders (SCID 1 and 2). This study suggests that 62.5% of female sex workers suffer from a mental health problem which is in accordance with previous studies. Mood and anxiety disorder were two of the most common, and there were also records of personality disorders among participants of this survey. There were also high rates of addiction in female sex workers of this study. Based on findings of this study, high rates of mental disorders such as personality disorders, anxiety disorder, and mood disorder were detected among female sex workers in the northwest of Iran. Financial incentive was reported to be the primary motivation for choosing sex work as a source of income.