This study aims to characterize trends and changes in the prevalence of knowledge of mother-to-child transmission (MTCT) means of HIV as well as to identify its associated socioeconomic factors among Vietnamese women. This is a repeated cross-sectional study using data from the Vietnam Multiple Indicator Cluster Surveys 2000, 2006, 2011 and 2014. We found that a slow increase was found in the trend of adequate knowledge of HIV transmission means from mother to child among women between 2000 and 2014 (41.81% in 2000, 45.66% in 2006, 49.58% in 2011, and 46.83% in 2014). Most women knew that HIV could be transmitted during pregnancy, however, more than half of women did not know all three ways of MTCT. Socioeconomic factors including age, ethnicity, education level, and economic status as factors that affected full knowledge of MTCT means. The study helps to design public health programs to raise 15-49-year-old women's knowledge in HIV transmission means from mother to child as well as can provide a quite strong case for policy adaptation to improve women's health in the time to come.