Extensive use of nanomaterials has greatly augmented their discharge into the environment and increased the potential risk to human and animal health by affecting the quality of the environment. Copper oxide nanostructures are extensively employed as antimicrobials, catalysts, surfactants, capacitors, and in other industrial and domestic applications. Copper oxide based NMs pose an environmental hazard due to their high production volumes and increasing use. Copper oxide nanostructures are used as antimicrobials, catalysts, surfactants, capacitors, and in other industrial and domestic applications. Due to their widespread production, copper oxide-based NMs pose an environmental risk. Environmental toxicity of NMs can differ dramatically depending on their physicochemical properties, i.e., dissolution, aggregation, and ROS generation, which are governed by the shape, size, capping agent, and stability. This study aimed to examine the potential toxicity of spherical copper oxide nanomaterials (CuO NMs) on the simple hydra model. Hydra magnipapillata 105, exposed to CuO NMs, displayed manifestation of toxicity in a dose and duration-dependent manner. Hydra, in the light of its ease of culture and testing and its sensitivity to contaminants, can be employed effectively as a model organism for risk assessment of chemicals and nanomaterials in aquatic environments.