<p>Cancer remains a significant global health challenge, affecting populations in both developed and developing countries. Increasing attention is being directed toward the potential of natural compounds as promising candidates in the search for effective cancer treatments. Dieckol, a marine-derived phlorotannin isolated from the brown algae <i>Ecklonia cava</i>, has garnered attention for its broad-spectrum bioactivities, particularly its anticancer potential. Dieckol demonstrates potent antioxidant and anti-inflammatory properties that help reduce oxidative stress and persistent inflammation, both of which are key contributors to tumor progression. It influences critical cellular processes such as apoptosis and autophagy, often triggering mitochondrial dysfunction and lysosomal impairment to induce cancer cell death. Dieckol has been shown to influence biotransformation enzymes and to restrict tumor invasion and metastasis by modulating matrix metalloproteinases (MMPs), vascular endothelial growth factor (VEGF), and tissue inhibitors of metalloproteinases (TIMPs). In addition, it disrupts multiple oncogenic signaling cascades such as PI3K/Akt/mTOR, NF-κB, JAK/STAT3, and FAK which collectively hinder cancer cell growth, survival, motility, and angiogenesis. The aim of this review is to provide an in-depth analysis of existing studies on dieckol, emphasizing its diverse mechanisms and potential in suppressing cancer progression. It further highlights current evidence, clarifies its molecular targets, and evaluates its prospects as a promising candidate for cancer prevention and therapy.</p>