Background Mobility is a key social determinant of health for female sex workers (FSWs). While extant research has focused on the adverse effects of mobility for FSWs, there are very few studies that have examined the multiple ways in which mobility may impact the lives of these mobile women from their perspective. This qualitative study aims to fill this gap by exploring how mobility impacts the lives, livelihoods, and HIV care and treatment from the perspectives of women living with HIV in two epidemic settings, the Dominican Republic and Tanzania.Methods We conducted two rounds of in-depth interviews with 12 Dominican women and 12 Tanzanian women who were 18 years plus, had an HIV-positive diagnosis, and reported having exchanged sex for money in the last month. We utilized thematic analysis with a focus on intra- and intercomparisons to observe patterns within and across the two contexts.ResultsWe identified a salient pattern of three thematic “mobility paradoxes,” which related to both disruptors and benefits of sex work mobility: (1) uncertainty versus autonomy: while sex work mobility often took place in contexts of vulnerability, which often led to women experiencing violence, it simultaneously benefitted women by allowing them to choose where they stayed and make plans on their terms; (2) financial insecurity versus profitability: although participants sometimes made less money than expected when they traveled for sex work, there was a powerful economic benefit for mobile women as it increased their likelihood of profitability; and (3) disorder and interruptions versus strategy and social support in HIV care and treatment: participants reported that they were sometimes inconsistent with their HIV appointments and medications when they traveled for sex work. On the other hand, mobility contributed to participants often becoming more strategic and creative in their HIV care and treatment and relying on one another for support.ConclusionsFindings indicate that sex work mobility is a nuanced, complex, and paradoxical phenomenon. Implications include the development of strengths-based and community empowerment mobile health initiatives tailored to mitigate disruptors of mobility while maximizing benefits for this population.