Melanoma is an aggressive malignancy with poor survival once metastatic. Although immune checkpoint inhibitors, particularly anti-programmed cell death protein-1 (PD-1) therapies, have improved outcomes, many patients remain refractory or develop resistance. Increasing evidence implies the gut microbiome as a key regulator of antitumor immunity, leading to interest in fecal microbiota transplantation (FMT) as a strategy to enhance immunotherapy efficacy, especially when derived from donors who previously responded to PD-1 blockade. A systematic review of 15 preclinical and clinical studies published between 2015 and 2025 was conducted using PubMed, Web of Science, Embase, and SJSM Library Resources. Included studies evaluated FMT in melanoma and reported clinical, immunologic, microbiome, and survival outcomes. Across three early-phase clinical trials involving 45 patients, FMT combined with anti-PD-1 therapy achieved an overall response rate of 65%, including 20% complete and 45% partial responses, with grade 3 immune-related adverse events occurring in approximately 10-15% of patients. Responders demonstrated sustained engraftment of donor-derived microbiota, characterized by enrichment of Bifidobacteriaceae, Ruminococcaceae, Lachnospiraceae, Faecalibacterium prausnitzii, and Akkermansia muciniphila, taxa associated with enhanced T-cell activation, improved mucosal integrity, and increased short-chain fatty acid production. Survival analyses revealed that low B-Raf expression was associated with longer survival in the absence of PD-1 therapy (32 vs. 24 months; p = 0.0512), while PD-1 treatment partially mitigated the adverse prognostic impact of high B-Raf expression (24 vs. 33 months; p = 0.0294). Longitudinal profiling showed that FMT-induced microbial changes persisted for 1-3 months in responders but regressed toward baseline in nonresponders, highlighting durable engraftment as a determinant of sustained benefit. Overall, FMT represents a feasible and biologically plausible adjunct to anti-PD-1 therapy in melanoma, with early evidence suggesting improved immune responsiveness and potential reversal of treatment resistance. Larger randomized trials are needed to optimize donor selection, confirm durability, and define long-term safety and mechanistic pathways.