Er2O3 nanorods were successfully prepared with hydrothermal treatment without using organic additives such as surfactant, fatty acid, or alcohol. Er2O3 nanorods were obtained under high temperature and/or long reaction times. Er2O3 nanorods mainly exposed {440} and {400} facets on the surface. Er2O3 nanorods showed excellent catalytic activity compared to commercial Er2O3 nanoparticles in the dehydration of 1,4-butanediol to produce 3-buten-1-ol.