Background: Despite the high potential to improve the quality of life of patients and families, palliative care services face significant obstacles to their use. In countries with high-resource health systems, the nonfinancial and nonstructural obstacles to palliative care services are particularly prominent. These are the cognitive barriers-knowledge and communication barriers-to the use of palliative care. To date no systematic review has given the deserved attention to the cognitive barriers and facilitators to palliative care services utilization. This study aims to synthesize knowledge on cognitive barriers and facilitators to palliative care use in oncology and hemato-oncology from the experiences of health professionals, patients, and their families. Methods: A systematic review was conducted. PubMed, PsycINFO, International Association for Hospice and Palliative Care/Cumulative Index of Nursing and Allied Health Literature (IAHPC/CINAHL), and Communication & Mass Media Complete (CMMC) were systematically searched for the main core concepts: palliative care, barriers, facilitators, perspectives, points of view, and related terms and synonyms. After screening of titles, abstracts, and full-texts, 52 studies were included in the qualitative thematic analysis.