Phenolics and terpenoids constitute one of the largest classes of phytochemicals with diverse chemical and structural architecture in plants. Biologically important sub-classes of phenolics include flavonoids, tannins, stilbenes, coumarins, and lignans, while those of terpenoids are the homo-, mono-, di-, sesqui-, tri-, tetra-, and poly-terpenoids. These phytochemicals potentiate several biological activities, including antidiabetic, antioxidant, anti-inflammatory, anticancer, antimicrobial, nephroprotective, antihyperlipidemic, and neuroprotective effects. The advent of nanotechnology and its significance in biomedicine is evident in the delivery of more effective diagnostic and therapeutic procedures. Incorporating phenolics and terpenoids into nanostructures significantly enhances their applications in biomedicine in the form of improved bioavailability, solubility, stability, controlled release, and targeted delivery, making them more effective in the treatment of diseases such as cancer and diabetes, as the concept holds remarkable promise for advancing therapeutic interventions. This chapter highlights not only the biomedical applications of phenolics and terpenoids and their nanostructures but also provides insights on the challenges and lays the premise for future research directions such as the incorporation of computational techniques, further preclinical and clinical studies, personalized medicine, toxicity profiling, and collaborative research in the use of phenolic and terpenoid nanostructures for improved biomedical outcomes.