During the last few decades, nanotechnology has gained many applications in almost all fields of life because of the unique properties of nanoparticles. Nanotechnology has specially marked its name in the field of medicine. However, nanoparticles toxicity is detrimental to human health and is a prime concern in applied medicine. They can cause insomnia, vertigo, madarosis, epistaxis, hypokalemia, lymphopenia, Alzheimer's and Parkinson's diseases, etc. There is a gap in knowledge regarding the study of the toxicological effects of nanoparticles. Mechanisms that are responsible for this toxicity are not fully understood yet. Phytochemicals have natural therapeutic effects of reducing metal nanoparticles' toxicity by acting as stabilizers and nontoxic reducing agents. However, the interaction between phytochemicals and nanoparticles is remained to be elucidated. This review will provide in-depth knowledge about the various types of inorganic nanoparticles and their associated toxicities, key parameters determining the toxic behaviour of nanoparticles, and the mechanisms behind their cytotoxicity. It also emphasizes the need for further research to understand the interaction between various phytochemicals and nanoparticles for therapeutic purposes.