Palliative care has received increasing attention at the American Society of Clinical Oncology (ASCO) Annual Meeting since the publication of its provisional clinical opinion on the topic in 2012. Despite frequent discussion, palliative care remains a source of some controversy and confusion in clinical practice, especially concerning who should provide it, what it encompasses, and when and how it can help patients and their families. In this article, we provide a formal definition of palliative care and review the state of the science of palliative care in oncology. Several randomized controlled trials now show that palliative care improves important outcomes for patients with cancer. Related outcome improvements include a reduction in symptoms, improved quality of life, better prognostic understanding, less depressed mood, less aggressive end-of-life care, reduced resource utilization, and even prolonged survival. As such, ASCO recommends early integration of palliative care into comprehensive cancer care for all patients with advanced disease and/or significant symptom burden. Our aim is that this summary will facilitate greater understanding about palliative care and encourage further integration of palliative care services into cancer care. More research is needed to illuminate the mechanisms of action of palliative care and to improve the specificity of palliative care applications to unique scenarios and populations in oncology.