ObjectiveCaregiving for a loved one is challenging and requires significant resources. Existential distress in family caregivers may include hopelessness, demoralization, fear of death, pre‐loss grief, or a sense of not being emotionally prepared. The aim of this systematic review is to synthesize the quantitative literature on existential distress among family caregivers of patients with advanced cancer, focusing on its prevalence, association with mental disorders, as well as with sociodemographic, disease, and treatment‐related factors.MethodsWe systematically searched electronic databases for quantitative studies of the above‐described existential distress concepts in family caregivers of patients with advanced cancer. Two independent reviewers extracted data and evaluated study quality. Data were analyzed using random‐effects meta‐analysis.ResultsWe retrieved 17.587 records, of which 31 studies fulfilled inclusion criteria. 63% of the studies (n = 20) provided sufficient data for meta‐analysis for 5558 patients. We found an overall pooled prevalence of 30.6% for existential distress, 95% CI [24.2–37.0]. For existential distress subconcepts, prevalence rates were 57.0%, 95% CI [37.8–76.2], for death anxiety, 13.9%, 95% CI [10.8–17.0], for demoralization, 24.0%, 95% CI [18.0–30.0], for pre‐loss grief, 18.4%, 95% CI [4.0–32.7], for hopelessness, 35.2%, 95% CI [28.2–42.2], for loneliness, and 35.6%, 95% CI [13.0–58.3], for emotional unpreparedness.ConclusionsApproximately one third of the respondents were affected by high levels of existential distress. The review provides evidence for further development of support services that can reduce existential distress, focused on death anxiety, and improve the quality of life for family caregivers of patients with advanced cancer.