AimsGlobally, women who use drugs often practice sex work and experience multiple health and social harms that complicate their drug treatment needs. In East Africa, understanding the emergence of heroin use among women is critical in efforts to build effective drug treatment programming, including the ongoing scale-up of medication-assisted treatment (MAT). We explored heroin use among women engaged in sex work in Kenya to inform services. MethodsIn a qualitative study of 45 female sex workers reporting substance use in Kisumu, Kenya, 32 reported lifetime heroin use and comprise the focus of this analysis. Semi-structured interviews explored histories of substance use and sex work and health programming needs. Thematic analysis focused on the contexts and meanings of heroin use. ResultsAmong 32 women, median age was 28 (range: 18–37). Women commonly smoked cocktails containing heroin while using alcohol and other drugs prior to sex work. Most women perceived heroin to engender “morale” and “courage” to engage in sex work and “fight” potentially abusive clients. Sex work reinforced drug use in ways that both managed and created new risks. ConclusionsDrawing on the concept of “paradoxical autonomy,” we suggest that heroin use engenders new forms of autonomy allowing women to support themselves in conditions of uncertainty, yet does not enable them to entirely overcome their vulnerabilities. Drug treatment programs for sex workers should address the situated logics of substance use in contexts of sexual risk, including patterns of poly-substance use that may render MAT inappropriate for some women who use heroin.