Background ‘HIV prevention cascades’ have been proposed to support programmes by identifying gaps in demand for, access to and capability to adhere to HIV prevention tools, but there are few empirical examples to guide development. We apply a prevention cascade framework to examine prevention coverage and factors associated with condoms and/or PrEP adherence among female sex workers (FSW). Setting Seven sites across Zimbabwe. Methods Seven respondent-driven sampling (RDS) surveys from the intervention sites of a pragmatic cluster-randomised trial in Zimbabwe in 2016 were analysed, and 611/1439 women testing HIV-negative included. We operationalised key components of an HIV prevention cascade including demand, supply and capability to adhere to two tools for HIV prevention: condoms and Pre-Exposure Prophylaxis (PrEP). We used adjusted logistic regression to identify determinants of adherence to condoms and PrEP in turn, examining the effect of adherence to one tool on adherence to the other. Results There were 343/611, 54.7%, women reporting adherence to condoms and/or PrEP, leaving almost half uncovered. While women were aware that condoms prevented HIV and reported good access to them, only 45·5% reported full adherence to condom use. For PrEP, a new technology, there were gaps along all three domains of demand, supply and adherence. Alcohol use decreased adherence to PrEP and condoms. Younger and newer entrants to sex work were less likely to take PrEP every day. Conclusion HIV prevention programming among FSW in Zimbabwe could consider increasing awareness of PrEP alongside supply, alcohol use interventions, and approaches to engaging younger women.