Cancer is considered the principal cause of death worldwide, with breast and lung cancer the most prevalent type in women and men, respectively. Cancer treatments, such as chemotherapy and radiotherapy, have disadvantages due to lack of selectivity toward tumor cells and inefficient drug delivery to tumor sites. Nanotechnology presents promising solutions to these limitations. In this sense, the use of nanocarriers can enhance the precision and efficacy of the treatment through innovative nano-based interventions. Nanoparticles have a wide application in medical contexts due to their size in which quantum phenomena take place. Therefore, they presented a high surface-to-mass ratio along with the ability to transport diverse compounds. They have the capacity to improve therapeutic efficacy and mitigate adverse effects through the enhancement of drug stability, reduction of adverse reactions, and modulation of pharmacokinetic profiles. Nanomedicine is emerging as a gateway for diagnostic and treatment strategies that overcome many obstacles faced by conventional therapies. Plant-based herbal medicines, natural compounds, and their derivatives are considered promising in cancer research and treatment. Several phytochemical groups such as polyphenols and their derivatives, naphtoquinones, and sesquiterpene lactones are under preclinical and clinical investigations in innovative drug delivery systems with the objective to enhance pharmacological parameters, such as bioavailability, efficacy, and safety. The elucidation of cancer biology has spurred advancements in nanoparticle-based drug delivery, offering potential benefits such as reduced toxicity, circumvention of multidrug resistance, and improved drug solubility. Consequently, the integration of immunotherapy with nanoparticles has emerged as a viable strategy to prevent tumor recurrence and metastasis. Concurrently, clinical trials are exploring combinations of conventional therapies with other modalities—immunotherapy, photothermal ablation, and gene therapy—as potential treatments for various tumors. This chapter provides a comprehensive analysis of preclinical and clinical investigations related to compounds of both natural and synthetic origin, integrated with different therapeutic approaches for the treatment of diverse tumors.