Engineered nanomaterials (ENMs) are increasing their presence in the worldwide market as display innovative properties that are suitable for various applications in many fields. In particular, TiO2 nanoparticles (nTiO2 ) are widely used in products accessible to the mass market. Nevertheless, there is a paucity of general information about their potential effects towards the aquatic species, especially to marine species. In this work the in vivo effects of TiO2 nanoparticles were checked with a battery of model organisms: V. fischeri, P. tricornutum, C. gigas and M. galloprovincialis. Moreover, ENMs bioaccumulation was investigated using the ragworm H. diversicolor. The comparison of results with literature highlighted some criticisms of toxicity tests with ENMs, mainly due to the difficulty of determining the real exposure scenarios.