Background The opioid epidemic is a progressively worsening public health crisis that continues to impact healthcare system strategies such as overdose reversal and destigmatization. Even among healthcare professionals, there remains a lack of confidence in naloxone administration and a prevalence of stigma. While training can play a major impact in reducing these shortcomings, the long-term effectiveness has yet to be characterized in training healthcare professionals. This study examined the long-term retention of opioid overdose awareness and reversal training (OOART) by evaluating performance at two-time intervals, immediately post-training and at a 3-month follow-up. Methods Voluntary training was offered to first-year (M1) medical students at the Drexel University College of Medicine in 2021. At this training, 118 students completed training, 95 completed the post-training survey, and 42 completed the 3-month follow-up. Results Opioid reversal knowledge questions assessed significantly increased scores post-training and at the 3-month follow-up. In three of the attitude questions, scores were improved at both follow-up timepoints. In addition, three attitude questions indicating a participant’s confidence to respond to an opioid overdose situation increased directly after the training, but regressed at the 3-month follow-up. The remaining questions did not show any statistical difference across the survey intervals. Conclusions This study establishes that while OOART provides participants with the knowledge of how to respond to an opioid overdose, the retention of this knowledge at a 3-month interval is reduced. The results were mixed for longitudinal assessment of participant’s attitudes toward people with opioid use disorder. Some positive increases in attitudes were retained at the 3-month interval, while others trended back toward pre-training levels. These results support the effectiveness of the training but also provide evidence that OOART must be reinforced often.