Immune checkpoint inhibitor (ICI)-associated hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory toxicity increasingly described in solid tumors, but evidence remains limited to case reports and small series. We systematically reviewed adult cases of ICI-associated HLH in solid malignancies identified through PubMed, Cochrane Library, Google Scholar, and reference-list screening from database inception through March 3, 2026. Case-level data were extracted for tumor type, ICI regimen, timing, diagnostic findings, HLH-directed therapy, ICU-level care, and outcomes; because of heterogeneity, findings were summarized descriptively. Eighty adult cases were included. Median age was 63 years; the most common cancers were lung cancer, melanoma, breast cancer, and renal tumors. PD-1 inhibitors predominated, mainly pembrolizumab and nivolumab. Among cases with reported timing, median time from last ICI dose to HLH onset was 17 days, with most occurring within 30 days of the last dose and within the first four ICI-containing cycles. Corticosteroids were used in nearly all cases; additional therapies included tocilizumab, etoposide, anakinra, IVIG, mycophenolate, ruxolitinib, calcineurin inhibitors, and plasma exchange. ICI-associated HLH often occurs early after exposure and may mimic sepsis, malignancy progression, or other immune-related adverse events; prospective data are needed to define risk factors, diagnostic thresholds, and treatment strategies.