Background: The comprehensive assessment of needs in palliative care identifies where patients most want attention to guide clinical decisions that tailor care provision from their first encounters. Aim: To define how and what needs are identified by the comprehensive assessment of needs in the original peer-reviewed articles in the field of palliative care. Design: An integrative systematic review as outlined by Whittemore and Knafl. Quality appraisal performed using the Mixed Methods Appraisal Tool. Data sources: PubMed, CINAHL, PsycINFO, Web of Science databases searched through May 2019 and updated in July 2020. Results: Forty-nine articles met inclusion criteria for original articles in English or Spanish reporting comprehensive assessment of needs of adult patients receiving palliative care. The majority (41/49) of studies were moderate to high quality. Two themes were identified: (1) How a comprehensive assessment of needs should be carried out in palliative care, which reflected a preference to develop structured tools for assessment; (2) What needs of patients should be assessed in the comprehensive assessment of needs in palliative care, which conveyed a trend to assess beyond core domains – physical, psychological, social, spiritual – with information and practical most prevalent, but with substantial variation in specifying and classifying needs into domains. Conclusions: The assessment of needs in palliative care is comprehensive but lacks consensus on the needs and domains that should be assessed by the palliative care team. Future studies should better define what needs can be standardized into the assessment to improve process of care and patient satisfaction.