BACKGROUND: Delirium is a distressing neuropsychiatric disorder affecting patients in palliative care. Although many delirium screening tools exist, their utility, and validation within palliative care settings has not undergone systematic review. AIM: To systematically review studies that validate delirium screening tools conducted in palliative care settings. DESIGN: Systematic review with narrative synthesis (PROSPERO ID: CRD42019125481). A risk of bias assessment via Quality Assessment Tool for Diagnostic Accuracy Studies-2 was performed. DATA SOURCES: Five electronic databases were systematically searched (January 1, 1982-May 3, 2020). Quantitative studies validating a screening tool in adult palliative care patient populations were included. Studies involving alcohol withdrawal, critical or perioperative care were excluded. RESULTS: Dual-reviewer screening of 3749 unique titles and abstracts identified 95 studies for full-text review and of these, 17 studies of 14 screening tools were included (n = 3496 patients). Data analyses revealed substantial heterogeneity in patient demographics and variability in screening and diagnostic practices that limited generalizability between study populations and care settings. A risk of bias assessment revealed methodological and reporting deficits, with only 3/17 studies at low risk of bias. CONCLUSIONS: The processes of selecting a delirium screening tool and determining optimal screening practices in palliative care are complex. One tool is unlikely to fit the needs of the entire palliative care population across all palliative care settings. Further research should be directed at evaluating and/or adapting screening tools and practices to fit the needs of specific palliative care settings and populations.