Vietnam aims to achieve full coverage of health insurance in 2015. An increasing type of health insurance in Vietnam is voluntary health insurance. Although there are many studies on the implementation of voluntary health insurance in Vietnam, little is known on the causal impact of voluntary health insurance. This paper measures the impact of voluntary health insurance on health care utilization and out-of-pocket payments using Vietnam Household Living Standard Surveys in 2004 and 2006. It was found out that voluntary health insurance helps the insured people increase the annual outpatient and inpatient visits by around 45% and 70%, respectively. However, the effect of voluntary health insurance on out-of-pocket expenses on health care services is not statistically significant. Copyright © 2011 John Wiley & Sons, Ltd.