Background: EP-CTs investigate novel therapeutic approaches for patients with cancer, but little is known about the use of supportive care services and timing of goals of care (GOC) discussions in EP-CTs. Methods: We conducted a retrospective review of consecutive patients with cancer enrolled on EP-CTs at Massachusetts General Hospital from 2017-2019. We collected information about patients’ demographic/clinical characteristics, use of supportive care services (palliative care [PC], social work [SW], physical therapy [PT], and nutrition), as well as documentation of GOC discussions and code status (before/during EP-CT vs after/never) via chart review. We examined patient characteristics associated with earlier receipt of supportive care services (before/during EP-CT vs after/never) and compared differences in the timing of GOC discussions and code status documented based on the receipt of supportive care services. Results: Among 425 patients enrolled on EP-CTs (median age 63.0; 56.0% female; 97.4% metastatic cancer; 22.1% gastrointestinal cancer), under half received supportive care services before/during trial (PC: 33.2% before/during, 66.8% post/never; SW: 41.9% before/during, 58.1% post/never; PT: 38.4% before/during, 61.6% post/never; and Nutrition: 33.2% before/during, 62.1% post/never). We identified the most common reasons for consulting each of the supportive care services (PC: 82.4% symptom management and 12.4% GOC; SW: 65.3% adjustment to illness and 23.8% referral for resources; PT: 44.8% safety/discharge planning and 24.6% mobility concerns; Nutrition: 73.2% for symptoms of anorexia/poor appetite and 21.5% nutrition assessment). Patients with GI cancer were more likely than those with other cancers to receive PC and SW before/during EP-CT (PC: 29.8% v 18.3%, p =.009; SW: 27.5% v 18.2%, p =.025). Earlier PC was associated with earlier hospice referral (HR = 1.95, p =.014) and shorter survival (HR = 1.54, p <.001). Patients receiving earlier supportive care services were more likely to have GOC discussions documented earlier (PC: 65.2% v 13.0%, p <.001; SW: 41.0% v 22.7%, p <.001; PT: 38.7% v 25.2%, p =.005; Nutrition: 39.1% v 25.0%, p =.002). Patients with earlier PC were more likely to have earlier documented code status (46.8% v 24.3%, p <.001), but not for any other service. Conclusions: In this cohort of patients with advanced cancer, under half received supportive care services before/during their participation in EP-CTs. We found that symptom management represented a common reason for referral to supportive care, highlighting the needs of this population. Patients who received earlier supportive care services were more likely to have earlier documentation of GOC discussions, with those receiving earlier PC having code status documented earlier and also experiencing earlier hospice use and shorter survival. These findings underscore the utility of supportive care services in EP-CTs.