Purpose: This meta-analysis aimed to summarize and synthesize the effectiveness of bereavement support for adult family caregivers in palliative care. Methods: Meta-analysis was conducted. The databases of the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane, Embase, Medline, PubMed, Scopus, and Web of Science were comprehensively searched from inception until January 2020. This study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and standard methods for conducting a meta-analysis. Data analysis was performed using Comprehensive Meta-analysis version 3.0, and the random-effects model was adopted. Findings: In total, 19 randomized controlled trials with an overall sample size of 2,690 participants met the inclusion criteria. The study showed that bereavement support had a significant effect on reducing grief (Hedges' g score = -0.198; 95% confidence interval [CI] -0.310 to -0.087), depression (Hedges' g score = -0.252; 95% CI -0.406 to -0.098), and anxiety (Hedges' g score = -0.153; 95% CI -0.283 to -0.023); however, high heterogeneity was present. No statistically significant difference was shown for traumatic feelings. Based on moderator analysis, a group format was more effective for grief, a combined individual and group format for depression, and an individual format for anxiety. Bereavement support was more effective when delivered by professionals, when delivered in more than six sessions, and need to be evaluated within 6 months. Conclusions: Bereavement support was effective in reducing grief, depression, and anxiety. The majority of the included studies had moderate heterogeneity, which limited the comparability of the evidence. Therefore, more robust randomized controlled trials are needed to confirm these study results. Clinical Relevance: This meta-analysis provides evidence that bereavement support delivered in the palliative care setting is effective for reducing grief, depression, and anxiety. Nurses and other healthcare professionals can make recommendations for adult family caregivers based on this study in reducing psychological symptoms due to a loss in the palliative care domain.