Palliative radiotherapy (PRT) is effective in alleviating the symptoms of many patients with advanced cancer, but there is evidence that it is underutilized, particularly in the elderly and in patients who live further from an RT center. Efforts to optimize access to PRT require an understanding of patterns of referral. The purpose of this study was to identify the sources of referral for PRT to a regional RT program. Our hypothesis is that the source of referral for PRT varies with the characteristics the patient. Medical and billing records were reviewed to identify the source of referral of patients who received PRT at a regional cancer center in Ontario between 2010 and 2015. Multivariate analysis was used to identify characteristics of the patient that are associated with the source of referral for PRT. Only the first course of PRT was considered. In total, 3,258 patients received PRT between 2010 and 2015. The patients’ median age was 70, 55% were male, and the median distance from patient residence to the radiotherapy center was 38.5 miles. The most common primary cancer sites were lung (37.2%), genitourinary (GU) (17.2%), gastrointestinal (GI) (12.8%), and breast (9.0%). PRT was given for locoregional disease in 36.0%, for distant metastases in 47.8%, and for indeterminate or multiple sites in 16.2%. Patients were referred by medical oncologists (MOs) (30.1%), other internists (26.4%), surgeons (24.2%), and family practitioners (FPs) (13.4%). In the remaining 5.9%, the need for PRT was identified by a radiation oncologist during follow-up after adjuvant or radical RT. The sources of PRT referrals varied significantly by primary cancer site (p<0.0001). Most lung cancer patients were referred by respirologists (34%), MOs (19%), or general internists (13%); most GU patients were referred by urologists (36%), FPs (20%), or MOs (19%); most GI patients were referred by MOs (47%), surgical oncologists (15%), or FPs (12%); and most breast patients were referred by MOs (61.2%), FPs (15%), or surgical oncologists (7%). The proportion of patents referred by their FP varied widely by disease site (range 7%-21%; p<0.0001). A multivariate analysis that controlled for primary site, showed that older patients were significantly more likely to be referred by their FP [>80 vs ≤60, OR 2.34 (1.67-3.27); 71-80 vs ≤60, OR 1.57 (1.15-2.14)], and that patients who lived further from the RT center were more likely be referred by their FP [>31 miles vs ≤31 miles, OR 1.37 (1.08-1.72)]. Diverse groups of doctors are involved in referring patients for PRT. Strategies for improving access to PRT should address the needs of specific patient groups by targeting the doctors who are most responsible for their care. FPs may be a key target for interventions aimed at enhancing access to PRT for older patients, and for those who reside further from an RT center.