This study developed an interview-based critical spatial thinking oral test and used the test to investigate the effects of Geographic Information System (GIS) learning on three components of critical spatial thinking: evaluating data reliability, exercising spatial reasoning, and assessing problem-solving validity. Thirty-two students at a large state university completed pre- and post-tests administered during the 2010 fall semester. This study found positive relationships between GIS learning and critical spatial thinking. We argue that the improvement can be attributed to students' experiences in a GIS course.