Background: Evidence shows that cancer patients are interested in learning about medicinal cannabis and frequently ask their oncologists for recommendations. To determine whether oncology training is adequately preparing physicians to address this topic, we conducted a national survey of oncology trainees to determine attitudes, practices, and knowledge about medical cannabis in cancer care. Methods: An interdisciplinary team developed an electronic questionnaire assessing trainees’ current practices regarding cannabis recommendations in cancer care and their knowledge of its effectiveness and risks compared with conventional care for cancer-related symptoms. We contacted 155 oncology training programs throughout the U.S. and asked that they distribute the survey to their trainees. Primary outcomes were: whether trainees reported discussing or recommending cannabis with/to patients and whether they felt sufficiently informed to make such recommendations. We presented data as proportions and used chi-square tests to compare proportions between groups. Results: Forty training programs from 25 states participated; of the 462 trainees in these programs, 187 completed surveys, yielding a response rate of 40%. Of the participants, 52% were female, 53% White, 33% Asian, and 5% Hispanic. One third (34%) graduated medical school before 2015, and 22% attended medical school outside the US. While 24% of trainees reported having received training regarding medical cannabis, only 12% felt sufficiently informed to make cannabis recommendations. Despite this, 91% reported having discussed cannabis with patients, and 58% reported recommending cannabis clinically to more than five patients in the prior year. Many viewed it as useful adjunctive therapy that was at least as effective as conventional treatments for: anorexia/cachexia (72%), nausea/vomiting (45%), and pain (41%). Over half (55%) believed that cannabis was beneficial to patients at the end of life; 31%, patients in active treatment; 11%, cancer survivors; 20%, the elderly with cancer and 16%, young adults with cancer. Peer-reviewed material (30%), lectures or webinars by another physician (29%), and patients and their families (22%) were the most commonly cited sources of information regarding medical cannabis. Oncologists who reported at least one area of focus as supportive/palliative care were more likely to feel sufficiently informed to make recommendations than oncologists without this focus (17% vs. 4%, P = 0.01); no other demographic or practice characteristics were associated with feeling sufficiently informed (all P > 0.10). Conclusions: Although most oncology trainees discuss cannabis use with their patients, the majority do not feel sufficiently informed about its use in cancer care. This represents an unmet need in contemporary oncology training, trainee satisfaction, and patient care.