Background: Early integration of palliative care for patients with advanced cancer has demonstrable benefits but is underutilized. We sought to characterize medical oncologists’ perspectives on palliative care and identify barriers to its early integration. Methods: A national sample of medical oncologists (N = 31) was recruited to participate in four focus groups. The focus groups were audio recorded, transcribed verbatim, and the transcripts were independently reviewed and coded by four investigators from diverse healthcare backgrounds (radiation oncology, critical care medicine, medical oncology, and public health). Sections of text were assigned a consensus code, and higher-level analysis was conducted to reveal concepts and themes. Results: Medical oncologists universally endorsed early clarification about the intent of chemotherapy (palliative versus curative). However, practice patterns related to palliative care integration and referral were variable. In this context, medical oncologists described themselves as “driving the bus” regarding the timing and utility of palliative care referral and end-of-life care planning. While medical oncologists acknowledged the evidence supporting early palliative care integration, numerous barriers to this practice were described. Medical oncologists reported patient-centered barriers such as patients’ perceptions of palliative care, the burden of extra physician visits, and copay costs. Additionally, many physician-centered barriers were voiced to justify underutilization of palliative care. Medical oncologists expressed ownership over patients’ care trajectory, and were concerned that palliative care physicians could interfere with the plan of care, provide inaccurate or misleading prognostic information, or offer options to patients that were not endorsed by the medical oncologist. Conclusions: Physician-centered concerns are potential barriers to the early integration of palliative care for patients with advanced cancer. These practice patterns may reduce patient autonomy and the benefits of early palliative care involvement.