A strong foundation in diagnostic imaging is essential to the practice of radiation oncology. This study evaluated radiology training in radiation oncology residency. An online survey was distributed to current radiation oncology residents in the USA by e-mail in 2017. Responses were summarized using frequency and percentages and compared with chi-square test and Spearman's rank correlation when appropriate. One hundred five residents completed the survey. Although most residents felt that a strong knowledge base in diagnostic radiology was moderately or extremely important (87%, n = 90/104), the majority were only somewhat confident in their radiology skills (61%, n = 63/104) and were only somewhat, minimally, or not at all satisfied with their training (79%, n = 81/103). Although there was an association between increasing post-graduate training and confidence level (p = 0.01062, ρ = 0.24959), the majority of graduating residents feel only somewhat confident in radiology skills (63%, n = 12/19). Residents were most commonly exposed to radiology via multidisciplinary conferences (96%, n = 100/104), though only 15% (n = 16/104) of residents ranked these as the most beneficial component of their radiology training and 13% (n = 13/101) of residents felt these were the least beneficial. Most residents (60%, n = 63/105) believe there is a need for dedicated radiology training during residency, preferring monthly formal didactics (68%, n = 71/105) co-taught by a radiologist and radiation oncologist (58%, n = 61/105). Radiation oncology residents feel their radiology training is suboptimal, suggesting a need for more guidance and standardization of radiology curriculum. A preferred option may be monthly didactics co-taught by radiologists and radiation oncologists; however, future studies should assess the effectiveness of this model.