The aim of this study is to measure the short-term impact of involuntary migration resulting from China's Three Gorges Dam project on the 1.3 million persons being displaced. We focus on the social, economic, and mental and physical health impact using three sets of indicators. Using a prospective research design, we gathered information about these indicators from a sample of migrants first before they moved and then again after they moved. Changes in the migrants' wellbeing during the period, when benchmarked to corresponding changes computed for a control group of non-migrants, are attributed to the impact of involuntary migration. Our results showed that although the displaced have enjoyed a relative gain in housing quality, most of the changes were in the negative direction and many of such negative changes were statistically significant.