This study investigates the pro-oxidant behavior of the antiepileptic drug carbamazepine (CBZ) on the marine algal species Dunaliella tertiolecta and the immune defense-related hemocytes of mussel Mytilus galloprovincialis. A phytotoxicity test, performed in a first step, showed a significant inhibition of the growth rate and the chlorophyll alpha (Chl-α) content in algae after exposure for 24 h to different concentrations of CBZ (1-200 mg L(-1)). On the other hand, the increased levels of lipid peroxidation products, such as MDA, measured in 24 h CBZ-treated cells were attenuated with time (48-96 h), followed by a significant recovery of both the algal growth rate and the Chl-α content in all cases. The latter could be related to the concomitant enhancement of total carotenoids in CBZ-treated algae with time, which in turn could protect algal growth and survival against CBZ-induced oxidative stress. On the other hand, the increased levels of cell death, superoxide anions ((·)O2 (-)), nitric oxides (NO, in terms of nitrites, NO2 (-)) and MDA content observed in mussel hemocytes exposed to environmentally relevant (0.01-1 μg L(-1)) and/or higher (10 and 100 μg L(-1)) concentrations of the drug, clearly indicate the ability of CBZ to induce oxidative effects on cells of non-target species, such as mussels, affecting thus their overall health status. The significant relationships occurred among the tested biological parameters in both bioassays, further reinforce CBZ-mediated pro-oxidant effects on species, widely used in ecotoxicological and toxicological studies and provide a more comprehensive view on its environmental fate and ecotoxicological risk evaluation.