This chapter reviews the available literature on the phytotoxic effects of nanomaterials on plant development, physiological behavior and molecular basis behind this phytotoxicity and nanoparticles (NP)-plant interaction. Due to their wider composition and nature, NPs present multiple functions and almost infinite applications in different fields such as biotechnology, biomedical, pharmaceuticals, cosmetics, electronics, optics, material science, textiles, energy sectors, water treatment technology, environmental remediation, and food and agriculture industry. Nanotechnology provides novel tools and techniques for delivery of genes and drug molecules to specific sites at cellular levels, and possesses great potential to augment crop productivity through genetic improvement of plants. Despite potential applications and benefits of nanotechnology in the agrifood sector, the extensive and indiscriminate use of NPs could lead to greater risk of their release into the environment, posing a serious threat to the ecological system and living beings including humans. Nanopesticides cover a wide variety of products including organic polymers, surfactants, and metal NPs.