In Vietnam, many medicine sellers serving pharmacies and retail outlets do not have adequate professional qualifications, and there has been a limited institutional control. The objective of this cross-sectional study was to examine the prevalence and determinants of self-medication among medicine sellers in Hanoi, Vietnam. Although 96.55% of medicine sellers had relatively serious health problems, only 61.21% visited a healthcare facility, though self-medication was moderately high (approximately 39%). Adopting Andersen's conceptual model, it was identified that medicine sellers who reported higher professional education, had low confidence in healthcare services, had not received any professional in-service during the prior year, had less serious health problems and who perceived the current costs of healthcare as too high were more likely to report self-medication. The findings have public health policy implications for these healthcare providers in urban Vietnam and other similar developing countries. Copyright © 2013 John Wiley & Sons, Ltd.