Background Patients with cancer have high symptom burden and unmet needs and therefore can benefit from palliative care. Oncology nurses are consistent providers of care to patients with cancer and can provide palliative care to these patients. However, oncology nurses' knowledge on palliative care has not been systematically evaluated. Objective To synthesize the current state of the science of oncology nurses' knowledge on palliative care. Methods A systematic literature search was completed using PubMed, Cumulative Index of Nursing and Allied Health Literature, and PsycINFO databases using the following key words: (oncology nurs*) AND (knowledge OR attitude OR belief OR perception) and (palliative care OR supportive care OR terminal care OR end-of-life care OR hospice). The quality of identified studies was rated on a 7-point scale using Fineout-Overholt's hierarchy of evidence. Results Twenty studies from 10 different countries were identified and synthesized for this review. Seventeen studies were quantitative, whereas 3 were qualitative studies. Results revealed that oncology nurses lacked knowledge on several aspects of palliative care. Conclusions Overall oncology nurses did not possess adequate knowledge on palliative care. Factors influencing oncology nurses' knowledge on palliative care included nurses' sociodemographic factors, educational status, years of experience, palliative care education/training, and clinical setting. Implications for practice This review provides evidence on gaps of oncology nurses' knowledge on palliative care and helps inform the design of interventions targeted toward enhancing oncology nurses' knowledge on palliative care.