Brief periods of wakeful resting have a positive effect on memory consolidation. To test the impact of mindful breathing exercises on the retention of new knowledge in a science class, we assigned lab sessions of Anatomy and Physiology I and II randomly to the intervention group or control group. During teaching periods, the intervention group lab sessions integrated mindfulness breaks by having students participate in guided breathing exercises every 25-30 minutes. With one exception, the average scores on the weekly retention quizzes taken at the end of the lab sessions were higher for the intervention group compared with the control group for all quizzes in both Anatomy and Physiology I and II. However, there was no significant difference in the average score between the intervention and control groups on formal quizzes and exams. Future studies should evaluate whether mindfulness techniques, such as mindful breathing exercises, used before exams lead to improved exam scores.