Background Patients with hematologic malignancies are less likely to receive specialist palliative care services than patients with solid tumors. Reasons for this difference are poorly understood. Methods This was a multisite, mixed-methods study to understand and contrast perceptions of palliative care among hematologic and solid tumor oncologists, using surveys assessing referral practices, and in-depth semi-structured interviews exploring views of palliative care. We compared referral patterns using standard statistical methods. We analyzed qualitative interview data using constant comparative methods, to explore reasons for observed differences. Results Among 66 interviewees, 23 oncologists cared exclusively for patients with hematologic malignancies; 43 treated only patients with solid tumors. Seven of 23 hematologic oncologists (30%) reported never referring to palliative care; all solid tumor oncologists had previously referred. In qualitative analyses, most hematologic oncologists viewed palliative care as end-of-life care, while most solid tumor oncologists viewed palliative care as a subspecialty that could assist with complex cases. Solid tumor oncologists emphasized practical barriers to palliative care referral, such as appointment availability and reimbursement issues. Hematologic oncologists emphasized philosophical concerns about palliative care referrals, including different treatment goals, responsiveness to chemotherapy, and a preference to control even palliative aspects of patient care. Conclusions Most hematologic oncologists view palliative care as end-of-life care, while solid tumor oncologists more often view palliative care as a subspecialty for co-managing complex patients. Efforts to integrate palliative care into hematologic malignancy practices will require solutions that address unique barriers to palliative care referral experienced by hematologic malignancy specialists.