Rosmarinic acid (RA), a polyphenolic compound found in herbs, such as rosemary, basil, and mint, has garnered significant attention due to its potent antioxidant and anticancer properties. This review examined the molecular mechanisms underlying these properties and their potential application in cancer prevention and therapy. It focuses specifically on RA’s role in modulating cancer-related pathways and presents a detailed analysis of recent advancements in this area. A systematic review of PubMed, Scopus, and Web of Science databases was conducted in accordance with PRISMA (Reporting Items for Systematic Reviews and Meta-Analysis) guidelines, focusing on studies published between 2019 and 2024. A total of 25 articles providing evidence from in vitro, in vivo, and in silico studies were selected. These findings elucidate the role of RA in inhibiting tumor cell proliferation, inducing apoptosis, and preventing metastasis in various types of cancer through diverse mechanisms, including its antioxidant properties. Despite these promising results, RA’s bioavailability challenges limit its therapeutic efficacy, underscoring the necessity for improved delivery methods. This review concludes that RA exhibits significant potential as a natural agent for cancer prevention and treatment, although further clinical trials are warranted.