The purpose of this study was to examine the impact of moderate- and high-fidelity patient simulator use on the critical thinking skills of associate degree nursing students. This quantitative study used a quasi-experimental design and the Health Sciences Reasoning Test (HSRT) to evaluate the critical thinking skills of third semester nursing students at two campus locations. Students in the simulation group had approximately 21% of the total traditional clinical hours replaced with simulation activities using moderate- and high-fidelity human patient simulators. Although all student groups demonstrated an increase in scores on the HSRT over the course of the semester, participants in the simulation group had significantly greater increases in deductive reasoning scores and participants in the traditional clinical group had significantly greater increases in total critical thinking scores. Further examination of the scores by campus demonstrated greater improvements in critical thinking scores in the simulation group on Campus A than for the traditional group on Campus A or either simulation or traditional clinical groups on Campus B. The Campus A simulation group demonstrated significant increases on deductive reasoning, analysis, and total critical thinking scores on the HSRT. This study indicated that well-constructed learning activities using moderate- and high-fidelity human patient simulators provide equal or better critical thinking outcomes in nursing students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]