Diabetes mellitus is rapidly rising worldwide, increasing almost twice over the last decades and burdening low- and middle-income countries. Rather than reducing hyperglycemia, the current approaches to the management of diabetes do not target the areas of oxidative stress, chronic inflammation, and progressive development of β-cell dysfunction (reduced insulin production by pancreatic β-cells). This calls for new, low-cost and sustainable interventions. Nanotechnology has the ability to provide fine control of drug delivery and solubility, and provide real-time glucose sensing. But traditional nanoparticle synthesis is frequently associated with the usage of toxic reagents and procedures that are expensive and prohibitively costly, bringing into question its safety and scalability. Medicinal plants have a high bioactive phytochemical content, such as flavonoids, alkaloids, terpenoids, and phenolics, and are in general underutilized candidates that can serve as a sound environmentally friendly alternative in the synthesis of nanoparticles. Green nanotechnology employs the plant components as the reducing and stabilizing agents in order to construct metal and metal oxide nanoparticles which incorporate phytochemical antidiabetic effects with the benefits of nanocarrier delivery systems. There is emerging evidence that plant-mediated nanoparticles have glucose uptake improvement, insulin sensitivity increase, reduced oxidative stress, as well as controlled and higher bioavailability.