Physicians trained in opioid use disorder (OUD) harm reduction can mitigate opioid overdose deaths by prescribing naloxone and educating patients about its use. Unfortunately, many physicians possess OUD stigma. Training during medical school presents an opportunity to reduce OUD stigma and improve opioid overdose reversal knowledge. This study assessed the efficacy of Opioid Overdose Awareness and Reversal Training (OOART) and evaluated the equivalency of the online and in-person OOART. Voluntary training was delivered to first-year medical (M1) students at one medical school. In 2018 and 2019, 29 and 68 M1 students, respectively, received in-person OOART training and completed pre- and post-training surveys. In 2020, 62 students participated in online OOART training, of which 53 completed both pre- and post-training surveys. All three opioid overdose Knowledge questions showed significant improvements between pre- and post-training survey responses. For Attitude questions, six of eleven questions in 2019 and 2020 and four of eleven questions in 2018 had statistically significant improvements between pre- and post-training survey responses. There were no statistical differences between in-person and online post-training survey results for two out of the three Knowledge questions and all 11 Attitude questions. This study demonstrates that our OOART was effective in increasing opioid overdose reversal knowledge and reducing OUD stigma. There was no meaningful difference in outcomes between the training modalities. These results support the future expansion of online and in-person OOART to a larger population of medical students.