Pre- and post-exposure prophylaxes (PrEP and PEP) can reduce the risk of HIV acquisition, yet often are inaccessible to and underutilized by most-vulnerable populations, including sex workers in sub-Saharan Africa. Based on in-depth interviews with 21 female and 23 male HIV-negative sex workers in Mombasa, Kenya, we found that awareness and knowledge of PrEP and PEP were low, although willingness to use both was high. Participants felt PrEP would be empowering and give added protection against infection, although some expressed concerns about side effects. Despite PEP's availability, few knew about it and even fewer had used it, but most who had would use it again. Sex workers valued confidentiality, privacy, trustworthiness, and convenient location in health services and wanted thorough HIV/STI assessments. These findings suggest the importance of situating PrEP and PEP within sex worker-friendly health services and conducting outreach to promote these biomedical prevention methods for Kenyan sex workers.