Future projections from the Intergovernmental Panel on Climate Change Report forecast an increase in anthropogenic atmospheric CO¬2 emissions, thereby exacerbating ocean acidification. Studies on CO2-induced acidification report evidence of its deleterious effect on behavioral alterations in marine fish species. One such disturbance affects behavioral lateralization, a function of brain asymmetry and a critical component to schooling performance. Though research has divulged the adverse behavioral effects of ocean acidification on stenohaline marine fishes, euryhaline models have not been explored to such extent. This study explored the combined effects of projected levels of pCO2 (~1300 ppm) and warming (+3.0oC) on behavioral lateralization in a euryhaline teleost, the adult Japanese ricefish (Oryzias latipes). After just five days of the treatment, CO2-treated fish exhibited significantly lower individual-level lateralization indices than that of fish in control CO2 (~300 ppm) and temperature, as well as no statistical difference to that of a random simulation. The implications are far-reaching even for highly efficient osmoregulatory fishes, in that coordination and schooling performance may be hampered at end-of-century conditions, thereby reducing fish population fitness.