<p>Cancer remains a major global health burden, with increasing incidence and limited access to effective and safe therapies. Isoorientin (ISO), a naturally occurring C-glucosyl flavone found in various medicinal plants, has garnered attention for its diverse pharmacological properties, particularly anticancer effects. This systematic review aims to critically evaluate and synthesize available in vitro and in vivo evidence on the anticancer potential of isoorientin across various cancer types. Following PRISMA guidelines, a systematic search was conducted in databases including PubMed, PMC, Scopus, ScienceDirect, Google Scholar, and Cochrane up to November 2025. Studies investigating the effects of isoorientin on apoptosis, cell cycle arrest, proliferation, migration, and invasion in cancer models were included. A total of 12 studies met the inclusion criteria. Isoorientin exhibited significant anticancer activity in multiple cancer types, including lung, liver, gastric, colorectal, pancreatic, and oral cancers. It induced apoptosis in a dose-dependent and time-dependent manner and caused G0/G1 or G2/M phase cell cycle arrest. Mechanistically, isoorientin modulated several signaling pathways such as MAPK, PI3K/Akt, AMPK, NF-κB, and Wnt/β-catenin. It also downregulated anti-apoptotic proteins (Bcl-2, Mcl-1) and upregulated pro-apoptotic markers (Bax, cytochrome c, caspases). Two xenograft studies confirmed its in vivo tumor-suppressive effects. Isoorientin demonstrates robust preclinical anticancer effects by targeting key pathways involved in apoptosis, proliferation, and metastasis. Further translational research, including clinical trials, is warranted to validate its therapeutic potential and safety profile in humans.</p>