Background: There is a lack of knowledge regarding medical marijuana use in cancer patients. More information is needed due to increase in both state approvals and access to medical marijuana. We hypothesized that variation in provider knowledge, attitudes, and behaviors exists across all professions in oncology, which contributes to a lack of both provider awareness of patient use and patient education on marijuana use. Methods: A survey was distributed to oncology providers in the state of Colorado. The primary objective was to describe provider knowledge, attitudes, and behaviors regarding medical marijuana use in cancer patients. Other objectives were identifying educational needs for oncology providers to feel comfortable recommending medical marijuana and reporting provider interest in future marijuana studies. Results: We received responses from 172 oncology providers; 48 advanced practice providers, 47 physicians, 53 registered nurses, 17 pharmacists, and 7 other. Most providers (73.3%) believe marijuana provides a medical benefit to cancer patients, and 81.5% believe it should be available as a prescription drug. Yet, 60.1% had not recommend its use to any cancer patient in the past 6 months, and 54.3% are not comfortable recommending or suggesting it to a patient to manage cancer related symptoms. Major concerns included uncertain dosing (83%), limited knowledge of available products and where to get them (73.1%), and interactions with other medications (64.9%). Providers reported that educational programs for healthcare providers (79.3%), more clinical data (74%), and endorsed clinical guidelines (67.5%) would increase their comfort level in recommending medical marijuana. The areas of research most interesting or important were specific product information and doses (77.6%), efficacy for specific side effects (77.6%), and drug-drug interactions (74.7%). Conclusions: Regardless of profession, the majority of oncology providers in Colorado do not recommend and do not feel comfortable recommending or suggesting medical marijuana to a cancer patient, yet most believe it provides medical benefit. Providers believe there is a need for education and research on the use of medical marijuana in oncology patients.