Heterogeneous photocatalysts are considered “green” and non-toxic materials for environmental remediation. Although nanosized photocatalysts can promote optimistic pollutant degradation rates, the assessment of their toxicity is highly recommended. In this work, NaY zeolite-supported Niobium oxides were synthesized by deposition, precipitation, and thermal hydration methods. Ecotoxicity tests with Artemia salina and phytotoxicity tests with Lactuca sativa were performed to evaluate the toxicity of the nanomaterials. Nb2O5 prepared by thermal hydration method was the lowest phytotoxic catalyst, but the most ecotoxic, with LC50 equal to 85 mg L-1. The presence of NaY reduced the toxicity of the oxides. The 10% Nb2O5/NaY material showed reduced toxicity and did not present an inhibition effect on the development of Lactuca sativa seeds. These findings suggest that the nanoparticles can have significant interaction with biological structures, emphasizing the importance of careful handling of this material, as it is not completely absent of toxicity.