<p>The wide applications of nanomaterials inevitably affect the aquatic environment. Due to the extensive usage of nano-copper carbon composite (NCCC) in different domains, such as water microbial control, textile industry, plastics processing industry, etc., it is necessary to investigate its effects on the aquatic environment. In this study, <i>Chlorella vulgaris</i> and <i>Scenedesmus</i> were applied as standard test algae species for toxicological evaluation of the aquatic environment. NCCC had persistent inhibitory effects on the growth of <i>Chlorella vulgaris</i> and <i>Scenedesmus</i>, via the release of Cu²⁺ and the excessive formation of ROS (reactive oxygen species). As the dosage of NCCC was up to 30 mg L^-1, microalgae growth was effectively suppressed during the 50-day exposure. The results of ROS levels and MDA (malondialdehyde) levels demonstrated that <i>Scenedesmus</i> was more sensitive to the toxicity of NCCC than <i>Chlorella vulgaris</i>. The fluorescein diacetate (FDA)-propidium iodide (PI) double staining method showed that the toxicity of 60 mg L^-1 NCCC only resulted in a small amount of algal cell death. In addition, with a comparable amount of Cu, NCCC was more toxic than CuSO₄, but had lower risks in the aquatic environment regarding the accumulation of Cu. The results presented here supply toxicity data of NCCC on microalgae, resulting in a suitable realization of its ecological behavior and influences.</p>