Early evidence shows that amphetamine-type stimulant (ATS) use has been rapidly increasing in Vietnam. Female sex workers (FSWs) who use ATSs have increased sexual risks for HIV infection. This paper presents qualitative data from a mixed-method study conducted from 2010 to 2011 that aimed to explore the use of ATS among FSWs in three major cities and to identify HIV-related sexual risks among this group. A total of 37 in-depth interviews were conducted, and thematic analysis was performed using NVIVO 8.0 software. Study participants reported that they perceive ATS to be more 'stylish', 'higher class' and much less 'addictive' than heroin. The study highlights multiple sexual risks among this group, including having prolonged sex; sex with multiple simultaneous partners or clients; lack of negotiation for safe sex; increased likelihood of group sex in the context of drug pooling and extended drug and sexual network; as well as unprotected sex. There is an urgent need to promote contextually appropriate interventions to reduce the HIV-related sexual risks among this group.