The present study examines the role of domestic migration in a massive demographic change in the Rio Grande Valley (RGV) of Texas with a special focus on ethnic composition of migration flows. Specifically, using two datasets derived from the Current Population Survey (CPS) and American Community Survey (ACS), this project: (1) outlines demographic profiles of domestic inbound and outbound migrants; (2) identifies determinants of migration for different types of movers; and (3) predicts the change in the Index of Dissimilarity (IT) at the census-tract level in the RGV. Results indicate that: (1) compared to stayers, Anglos were overrepresented among all migrant categories in the RGV; (2) leavers were likely to be motivated by career/employment opportunities outside the Valley, while affordable housing in the Valley was the primary motivating factor for newcomers; (3) recently arrived Hispanic immigrants became more segregated. The most important finding is that, compared to Hispanics, Anglos were not ‘pushed’ from the Valley by a growing Mexican-American population but became more segregated