Traditional cancer therapies, despite their long-standing use, are fraught with drawbacks, often leading to limited efficacy and severe side effects. Chemotherapy, a cornerstone in cancer treatment, lacks specificity, causing collateral damage to healthy cells and resulting in debilitating adverse effects. Radiotherapy, while effective in targeting localized tumors, may inadvertently harm the surrounding tissues. Additionally, both treatments can elicit resistance mechanisms in cancer cells over time, diminishing their long-term effectiveness. RNA interference (RNAi) emerges as a promising alternative with the potential to overcome these drawbacks. Its remarkable precision in targeting cancer-related genes allows for a more specific and tailored approach, minimizing damage to healthy tissues. This precision is crucial in addressing the challenges associated with tumor resistance to traditional chemotherapy and radiotherapy. An array of innovative delivery systems is being explored to capitalize on RNAi’s therapeutic potential fully. Lipid nanoparticles (LNPs) protect and target RNA molecules in cancer cells, enhancing RNAi therapy’s precision. Viral vectors, like adeno-associated viruses (AAVs) and lentiviruses, enable sustained RNA expression in target cells. Nonviral systems, such as cationic polymers and liposomes, aid RNA delivery by forming complexes or encapsulating RNA for targeted delivery. Developing these advanced delivery systems addresses the challenge of ensuring the stability of RNAi payloads during systemic circulation and enhances their therapeutic efficacy. While RNAi holds great promise for personalized cancer therapy, the journey from discovery to pharmaceutical success is not without hurdles. Delivery system optimization, minimizing potential off-target effects, and ensuring sustained therapeutic effects remain ongoing challenges. This chapter explores the triumphs and the intricate challenges encountered in harnessing RNA interference for cancer therapy in the contemporary medical landscape.