Exposure to polycyclic aromatic hydrocarbons (PAH) negatively impacts exercise performance in fish species but the physiological modifications that result in this phenotype are poorly understood. Prior studies have shown that embryonic and juvenile mahi-mahi (Coryphaeus hippurus) exposed to PAH exhibit morphological abnormalities, altered cardiac development and reduced swimming performance. It has been suggested that cardiovascular function inhibited by PAH exposure accounts for the compromised exercise performance in fish species. In this study we used in-situ techniques to measure hemodynamic responses of young adult mahi-mahi exposed to PAH for 24h. The data indicate that stroke volume was reduced 44% in mahi-mahi exposed to 9.6±2.7μgl-1 geometric mean PAH (∑PAH) and resulted in a 39% reduction in cardiac output and a 52% reduction in stroke work. Maximal change in pressure over change in time was 28% lower in mahi-mahi exposed to this level of ∑PAH. Mean intraventricular pressures and heart rate were not significantly changed. This study suggests exposure to environmentally relevant PAH concentrations impairs aspects of cardiovascular function in mahi-mahi.