The influence of fuel aromatic content and type on the exhaust emissions from a heavy-duty diesel engine were investigated by blending predetermined amounts of aromatic compounds with a known chemical structure into a low-aromatic base fuel. Seven test fuels were blended with constant cetane numbers and densities, but with mono-, di-, and tri-aromatic contents ranging from 10 to 30%, 0 to 10%, and 0 to 8%, respectively. The engine experiments were run using the AVL eight-mode steady-state simulation of the EPA transient test procedure. The results show that fuel total aromatic content or type did not significantly affect the engine’s PM emissions. NOx emissions, however, increased by 4.3% as the fuel mono-aromatic content increased from 10 to 30%.