Although many public hospital physicians in Vietnam offer private service on the side, little is known about the magnitude and nature of the phenomenon so-called dual practice, let alone the dynamics between the public and private health sectors. This study investigates how and to what degree public hospital physicians engage in private practice. It also examines the commitment of dual practitioners to the public sector. The analysis is based on a hospital-based survey of 483 physicians at 10 public hospitals in four provinces of Vietnam. Nearly half of the participants in the study sample reported themselves as dual practitioners. Various types of private practice were mentioned. Private practice at health facilities owned by the private sector was the most prevalent, followed by private practice delivered at health facilities owned by the dual practitioners themselves. Private practice inside public hospitals was also noted. Dual practitioners were likely to be senior and hold management positions inside their public hospitals. Substantial income differences were found between dual practitioners and those physicians practicing exclusively in the public sector. The majority of dual practitioners, however, reported the willingness to give up private practice if certain conditions were met, such as a basic salary increase or non-pecuniary benefits. The main reasons dual practitioners gave for not leaving the public sector included a sense of public responsibility and opportunities to gain a broader professional network and more training. This study reiterates the significant challenges associated with dual practice, including its financial implications and possible effects on health care quality and access. The need for a high-quality workforce committed to the public sector is particularly critical, given the possibility of universal insurance coverage. Future research should address the need to improve data collection on physicians’ dual practice and incorporate the topic in policy debates on health reform.