Cancer is a leading cause of mortality worldwide, primarily driven by uncontrolled cell proliferation, metastasis, and resistance to conventional therapies. Natural bioactive compounds have gained attention as safer and potentially effective complements to synthetic drugs. Sulforaphane (SFN), an isothiocyanate generated from glucoraphanin in cruciferous vegetables such as broccoli, cabbage, and cauliflower, has emerged as a promising anticancer agent. This review examines the structural properties, natural sources, extraction strategies, pharmacokinetics, and therapeutic mechanisms of SFN in cancer prevention and treatment. Advances in solvent-based, microwave-assisted, ultrasound-assisted, high-pressure, and green-solvent extraction have improved SFN recovery and purity. Mechanistically, SFN modulates carcinogen metabolism, inhibits phase I enzymes, induces phase II detoxification enzymes, activates Keap1-Nrf2-ARE signaling, regulates epigenetic modifications, and triggers apoptosis through intrinsic and extrinsic pathways. Preclinical studies indicate that SFN can suppress tumor initiation, progression, angiogenesis, and metastasis across multiple cancer types. Nanocarrier-based delivery systems, particularly polymeric micelles and related formulations, may further enhance stability, bioavailability, and targeted release. Collectively, SFN represents a promising nutraceutical and adjunctive therapeutic candidate. Future research should prioritize standardized extraction, dose optimization, long-term safety evaluation, and well-designed clinical trials.