The contribution of nanotechnology has grown significantly since the last century, and numerous reports highlighted its potential in various arenas. Being economically feasible, nanotechnology finds its generous application in diverse domains including medicine, bioimaging, biosensing, electrical devices and in remediating pollutants from environment. However, in contrast, there had been significant arguments over its stability and ecotoxicity which need to be pondered for its long-term affliction over human health. The harsh chemicals and other conditions, including high temperature and large amount of water and heat, were required for the synthesis of the nanoparticles. Subsequently, in turn, huge amounts of robust chemicals, heat, and toxic by-products were released into the environment as well. These result in bioaccumulation and transfer of nanoparticles into different trophic levels which consequently can lead to major health hazards including immune-modulatory defects, oxidative stress, and mortality. Hence, the ill-fated impact of metal nanoparticles and carbon-based nanomaterials on human health, flora, and fauna is the major module to be discussed in this chapter.