Tralopyril (TLP) is a newly emerged antifouling biocide which rapidly degrades in water. The scientific data on its possible adverse effects to biota is very limited, and even more limited is the ecotoxicity data of its degradation products (DPs). In the present study we investigated the toxicity of TLP and its two main DPs on fertilization and embryogenesis of three sea urchin species: Clypeaster japonicus, Pseudocentrotus depressus and Hemicentrotus pulcherrimus. The species sensitivity to chemicals was investigated and compared. Additionally, the stability of TLP in test medium was examined. TLP in test medium degraded into one single degradation product. The degradation was slower at 17 °C (average incubation temperature for winter species H. pulcherrimus) than at 20 °C (incubation temperature for the other two species). Both DPs at 100 μg/L did not appear toxic, however, TLP highly affected larval development of all tested species. Sensitivity was similar for C. japonicus and P. depressus, but higher toxicity was noticed for H. pulcherrimus. The increased TLP toxicity on exposed H. pulcherrimus embryos could be attributed to the higher TLP stability at lower incubation temperature. Results suggest higher vulnerability to TLP for species spawning in colder seasons. Fertilization test appeared to be less sensitive than the embryotoxicity test.