Plants have demonstrated potential in providing various types of phytomedicines with chemopreventive properties that can combat prostate cancer. However, despite their promising in vitro activity, the incorporation of these phytochemicals into the market as anticancer agents has been hindered by their poor bioavailability, mainly due to their inadequate aqueous solubility, chemical instability, and unsatisfactory circulation time. To overcome these drawbacks, it has been suggested that the incorporation of phytochemicals as nanoparticles can offer a solution. The use of plant-based chemicals can also improve the biocompatibility of the formulated nanoparticles by avoiding the use of certain hazardous chemicals in the synthesis, leading to decreased toxicity in vivo. Moreover, in some cases, phytochemicals can act as targeting agents to tumour sites. This review will focus on and summarize the following points: the different types of nanoparticles that contain individual phytochemicals or plant extracts in their design with the aim of improving the bioavailability of the phytochemicals; the therapeutic evaluation of these nanoparticles against prostate cancer both in vitro and in vivo and the reported mode of action and the different types of anticancer experiments used; how the phytochemicals can also improve the targeting effects of these nanoparticles in some instances; and the potential toxicity of these nanoparticles.