This qualitative study was conducted to explore health-seeking behaviour for sexually transmitted infections (STIs) and HIV testing among female sex workers (FSWs) in the cities of Hanoi and Da Nang, Vietnam. Data were gathered from in-depth interviews, focus groups and participant observation. Results suggest that women's decision to seek STI treatment and HIV testing is influenced by the complex interplay of personal risk perceptions, social relationships and community discourse. The women exhibited adequate knowledge of HIV while their knowledge of STIs was limited. They demonstrated high-risk perceptions of HIV, but they showed little concern for STIs. Most women sought treatment at pharmacies when they noticed symptoms of the genital tract. Their decision to seek care in health facilities and HIV testing was hampered by the high costs of treatment, judgmental attitudes of service providers, and a lack of information on testing services. Future interventions need to focus on strengthening knowledge of STIs and the STI-HIV association, and increasing awareness of HIV counselling and testing services. Training for STI service providers including pharmacies and private practitioners on sex-worker friendly and non-judgmental services and counselling skills should be emphasized to provide timely diagnosis and treatment of STIs, and to refer women to HIV testing.