INTRODUCTION: Young female sex workers (FSWs) are at greater HIV risk than their older counterparts. Yet, the extent of their engagement with HIV services is largely unknown. We compared engagement among FSWs aged 18-24 years with those 25 years and older. METHODS: We used respondent-driven sampling to recruit FSWs from 14 communities in Zimbabwe from November to December 2013. We collected data on demographics, behavior, service uptake, and HIV and viral load testing. Data were pooled and weighted using respondent-driven sampling-2 estimation. We analyzed HIV care cascade variables by age group. To identify potential drivers of younger FSW service use, we explored factors associated with knowing one's HIV status. RESULTS: Among 2617 participants, mean age was 31 years and 26% were 18-24 years. Over half of FSWs initiated sex work before the age of 25 years. Overall HIV prevalence was 59% but was lower among younger FSWs (35% vs 67%, P < 0.01). Younger HIV-infected FSWs were significantly less engaged at each step of the care cascade. Among younger FSWs reporting antiretroviral therapy use, 62% had an undetectable viral load compared with 79% in older FSWs. In multivariable regression, young FSWs encouraged to have an HIV test by another FSW (adjusted odds ratio = 2.54; 95% confidence interval: 1.44 to 4.50), and those with no recent clients (adjusted odds ratio = 4.31; 95% confidence interval: 1.30 to 14.33) were more likely to report knowing their status. CONCLUSIONS: The high proportion of FSWs initiating sex work before the age of 25 years and their lower engagement in HIV services highlights the importance of considering this vulnerable population in HIV programming. Implementing targeted services tailored to the unique needs of young FSWs is a public health imperative.