The purpose of the present study is to assess prevalance and risk facors of mental health problems,rnsubstance abuse and coping mechanisms among Addis Ababa Street based female sex workers.rnMixed method explanatory research design was employed on 378 randomly selected street based sexrnworkers in ten nominated hotspot areas in Addis Ababa. Mental Health Inventory (MHI)-38, simplernscreening instrument for substance abuse (SSI-SA) and Brief Coping-28 were employed forrnassessment. FGD and interviews were also utilized. Descriptive statistics, independent t-test, Pearsonrncorrelation and ANOVA were utilized to analyze the quantitative collected data.rnAs a result, the general lifetime prevalence of psychological distress and substance abuse disorderrnamong street based sex workers was 35.4% and 75.1% respectively. Among the dimensions of mentalrnhealth index, depression, anxiety and loss of behavioral/emotional state was observed respectively.rnEven higher prevalence of psychological distress and substance abuse disorder was found amongrndivorced, illiterates, lower income, rural born, adolescence and sex workers who had a forensicrnhistory. As the cause to join the sex work, peer pressure, to improve personal and family lifernsituation, poverty and poor life situation of the families, to search for better life and better paying job,rnto failure to succeed in educational endeavors, unemployment, to get initial capital to start a business,rnsuccess of others, failed marriage and other reasons were highly reported major multifacetedrndeterminant factors for joining street based commercial sex worker.rnAs contributing factors for psychological distress, forced self-degrading type of sex by clients, forcedrnsex at knifepoint, physical assault, robbery, forced sex with multiple individuals at the same time.rnSometimes clients refuse to pay for the service they received, insulting, some take them to anrnunknown place and torture them for more than 3 days while doing anything they want to them, andrnsome injure them while they drunk were highly reported risk factors for developing psychosocialrnproblem among street based sex workers. In this study, place of birth, forensic history, childhoodrnhistory of sexual abuse, age, educational status, average monthly income and parentâ€™s livingrnarrangement had a statistically significant effect on mental health index of street based sex workers.rnFinally, the most frequently used adaptive coping mechanism by the sex workers were acceptancernand religion respectively. Instrumental support, emotional support, planning, positive reframing,rnactive coping and homer were also repeatedly reported adaptive coping mechanisms by sex workersrnin their due order. Concurrently, the most frequently used maladaptive coping mechanism by the sexrnworkers were self-blame and substance use. Along with this, venting, Self-distraction, denial,rnbehavioral disengagement were highly reported maladaptive coping mechanism by street based sexrnworkers respectively. In conclusion, the life time prevalence rate of psychological distress andrnsubstance abuse disorder were very high. Therefore, mental health service providers shall consider inrndiagnosing and treating psychosocial problems of street based sex worker.rnKey Word: Psychological distress, Psychological Wellbeing, substance abuse, sex work