<p>Titanium dioxide (TiO₂) in the form of nanoparticles has become a part of human daily life, and these nanoparticles (NPs) are now widely used in many fields. Also, its high environmental concentrations predicted to accumulate in aquatic ecosystems are cause for concern. Ecotoxicological tests have used sea urchins as models as they have more than 70% genome homology and metabolic similarity with higher vertebrates including humans. Following the green and chemical synthesis of TiO₂ NPs, the characterization was made by using UV–Vis spectrophotometer, X-ray diffraction, and transmission electron microscopy TEM. The sea urchin embryo was exposed to TiO₂ NPs (5, 50, and 500&#xa0;µg/l) in two experiments as embryotoxicity and spermiotoxicity for 2, 12, 24, and 48&#xa0;h. The exposed embryo to the green and chemically synthesized TiO₂ NPs in embryotoxicity and spermiotoxicity studies after all examined periods showed a significant increase in malondialdehyde and nitric oxide concentrations and a significant decrease in antioxidant markers compared to the control group. Light and scanning electron microscopic examinations revealed morphological alterations and abnormalities in the developmental stages of sea urchin embryos as a result of exposure to TiO₂ NPs. The current study determined that <i>Paracentrotus lividus</i> presents an excellent model organism for the aquatic environment. After all examined periods, the embryo that was exposed to the green and chemically synthesized TiO₂ NPs in the embryotoxicity and spermiotoxicity investigations exhibited a substantial oxidative stress status and damaged embryo at all stages.</p>