Critical thinking ability is required for safe nursing practice and nursing scholars agree that nursing students must learn critical thinking skills, however a consensus of how to best teach critical thinking is not readily available from the literature. Additionally, the need to assess and measure critical thinking skills is clear but research on methods of achieving this mandate is limited. The aim of this research study is to test the impact of an intervention applied during the preceptorship experience. The Health Science Reasoning Test (HSRT), a type of California Critical Thinking Skills Test (CCTST); was administered to two groups of nursing students from difference college enrolled in a NUR Preceptorship course. Following the administration of the HSRT the experimental group received the intervention of directions on journaling of response to clinical events; the control group did not receive an intervention. The HSRT was administered again to both groups at the completion of the preceptorship experience and the scores analyzed to determine the impact of the intervention. Specifically, the purpose was to determine if the use of guided reflective journaling resulted in a statistically significant difference in scores on a test of critical thinking.