Cerium (IV) oxide nanoparticles (NP CeO2) have a wide variety of applications including as a component in functional coating, in electronics, engineering, medicine, and are present in the environment as secondary products of combustion engines due to their use as fuel additives. It is the latter which may be of particular concern as the environmental load deriving from automobile exhaust is expected over the coming years to be significant. The aim of this work was to investigate the potential embryotoxicity of NP CeO2 on three sea urchin species: Arbacia lixula, Paracentrotus lividus and Sphaerechinus granularis using the sea urchin embryo development test (SUEDT). Embryonal development following the exposure of zygotes to NP CeO2 at concentrations ranging between 10 - 10000 μg/L proceeded for all three species without significant differences compared to the control. Sea urchin sperm was treated with NP CeO2 at the same concentrations as for the zygotes and results indicated that NP CeO2 did not affect the fertilization ability of sea urchin sperm, with more than 90% of eggs for each species successfully fertilized. These eggs developed into morphologically normal larvae at all NP concentrations except for the 10000 μg/L NP CeO2 treatment where larvae of A. lixula and P. lividus showed only 74.25 ± 8.42% and 82.25 ± 2.63% normally developed larvae after 48h, respectively. Thus, the sea urchin embryo development test did not indicate that the investigated NP CeO2 is a material of concern, even at high concentrations. However, a broader range of 57 bioassays must be conducted before concerns about the potential toxicity of cerium oxide nanoparticles may be completely alleviated.