The purpose of this study was to assess the impact interactive, online case studies have on learning for preservice teachers. More specifically, it evaluated whether the use of online case studies in instruction could enhance the level of knowledge the preservice teacher gained from the content material. This study utilized a nonequivalent group, pretest-posttest comparison design in an effort to analyze the impact of the online case studies in increasing teachers' depth of knowledge. One-hundred and fifty students enrolled in teacher preparation programs at three universities in two states participated. The experimental group, who interacted with the case studies, showed significant differences in their posttest performance. Their mean score on Abstract questions on the posttest was significantly higher than that of the comparison group, who did not interact with the case studies. This finding in combination with student feedback suggests subjects gained a higher level of understanding and application knowledge through interacting with the online case studies. Much of the literature supporting the use of case study methods in teacher preparation focuses on satisfaction, lacking outcome-related data. The results of this study demonstrate a significant, measurable change in teacher learning based on the use of online case studies.