Cu, Fe and Cu + Fe ion exchanged Beta and SSZ-13 catalysts were prepared by solution ion exchange using commercial NH4/Beta, and NH4/SSZ-13 that was prepared in-house. To study hydrothermal aging effects, Beta supported catalysts were aged hydrothermally at 700 degrees C and SSZ-13 supported catalysts were aged at 750 degrees C. In order to reveal the effects of Fe addition in the co-exchanged catalysts, these catalysts were characterized by means of powder X-ray diffraction (XRD), N2 adsorption-desorption, electron paramagnetic resonance (EPR), Al-27-nuclear magnetic resonance (Al-27-NMR) and propylene coking followed with temperature programmed reaction (TPR), and further tested with standard NH3-SCR with and without the presence of propylene. Collectively, the catalyst characterizations and reaction testing indicated minor beneficial effects of Fe addition in Cu, Fe/Beta, where NH3-SCR activity, N-2 selectivity and hydrothermal stability were all slightly improved. In contrast, Fe addition did not show apparent beneficial effects in low-temperature SCR for the Cu, Fe/SSZ-13 case. At elevated reaction temperatures, however, the presence of Fe indeed considerably improved NO conversion and N-2 selectivity for the hydrothermally aged Cu, Fe/SSZ-13 catalyst in the presence of propylene.