Nanotechnology is a science of producing and utilizing nanosized particles that are measured in nanometers. The unique size-dependent properties make the nanoparticles superior and indispensable as they show unusual physical, chemical, and properties such as conductivity, heat transfer, melting temperature, optical properties, and magnetization. Taking the advantages of these singular properties in order to develop new products is the main purpose of nanotechnology, and that is why it is regarded as “the next industrial revolution.” Although nanotechnology is quite a recent discipline, there have already high number of publications which discuss this topic. However, the safety of nanomaterials is of high priority. Whereas toxicity focuses on human beings and aims at protecting individuals, ecotoxicity looks at various trophic organism levels and intend to protect populations and ecosystems. Ecotoxicity includes natural uptake mechanisms and the influence of environmental factors on bioavailability (and thereby on toxicity). The present paper focuses on the ecotoxic effects and mechanisms of nanomaterials on microorganisms, plants, and other organisms including humans.