Vietnam's economy and education system have had remarkable success in recent decades, yet there are concerns about the declining returns to higher education since 2008. We document this decline in returns to higher education and propose four hypotheses to explain it. Analysis of the VLSS/VHLSS and LFS data provides little evidence for three of four hypotheses. The fourth hypothesis is that changes in the demand for highly educated labor in Vietnam, perhaps due to recent changes in foreign direct investment inflows, rather than the labor supply, are perhaps the most important determinant of the returns to education across different levels.