Cerium oxide nanoparticles (CeO₂ NPs) contain a number of properties suitable for biomedical, environmental and cosmetic applications, and in fact, they are well-known as inorganic sunscreen agents. Recently, cerium aminoclay (CeAC) has been considered as a hybrid material for sunscreen application, however, the basic information on the toxicity and oxidative stress induced by CeAC and CeO₂ NPs on cell lines remains scanty. Therefore, the present study performed an MTT assay and ROS measurement to assess the cell viability and oxidative stress on HaCaT cells. The results showed that CeAC and CeO₂ NPs exhibited low toxicities (IC50 values of 88.74/86.95 μg/mL and 84.13/83.13 μg/mL for 24 and 48 h, respectively). In particular, CeAC showed less toxicity than that did CeO₂, due to its larger size, resulting in less penetration into the cell membrane, which fact reduced the level of toxicity. Notably, the coexistence of Ce3+ and Ce4+ oxidation states has been shown to promote the antioxidant activity of Ce nanomaterials, playing a major role in enhancing radical scavenging as well as reducing the intracellular ROS level on HaCaT cells. According to this estimates, CeAC and CeO₂ NPs can be considered to be promising candidates for future cosmetic applications, especially sunscreens.