Female sex workers (FSWs) in Nepal continue to be disproportionately at risk for Sexually Transmitted Infections (STIs), including HIV. Due to stigma related to sex work and HIV, FSWs keep their sex work information hidden, which poses a barrier to seeking health services. Emerging research indicates a high uptake of mobile phones among FSWs in Nepal. Mobile health (mHealth) interventions can provide health information and linkage to care. However, largely missing from the literature is FSWs' experience of managing the information about their involvement in sex work in a culture where sharing personal information and belongings is a part of the social norm, and maintaining privacy could have negative social repercussions. The current study aims to understand how FSWs perceive and manage privacy when they share their mobile phones. Using the Communication Privacy Management theory, we explore FSWs' perception of the threat to their privacy posed by mobile phones. We conducted 30 in-depth interviews among FSWs in Kathmandu, Nepal. Results showed that all participants owned mobile phones, and sharing devices was common. Mobile phones pose a considerable challenge in keeping sex work information private, and FSWs use various communication strategies to circumvent privacy threats. The findings highlight the mental and emotional burden FSWs face trying to conceal their private information in a sharing culture. The study discusses the importance of theorizing privacy in the cultural context of the Global South and the practical implications for developing mHealth interventions for this population.