During the wet oxidation of contaminated wastewaters, the destruction of low molecular weight carboxylic acid intermediates such as acetic, glyoxalic, and oxalic acids is often the rate-controlling step. Oxidation of acetic acid, a very recalcitrant intermediate, requires compelling treatment severity. Heterogeneous catalytic wet oxidation of model acetic acid aqueous solutions was conducted under mild conditions (below the normal boiling point of water) using hydrogen peroxide over various transition metal-exchanged NaY zeolites. Treatment of Cu2+-NaY with oxalic acid [OA] led to a catalyst, Cu2+-NaY [OA], with significantly improved properties in terms of total organic carbon (TOC) removal efficiency and catalyst stability against leaching. This catalyst outperformed homogeneous Cu2+ by a factor of 2-2.5 times. Continuous feeding of H2O2 reduced its undesirable decomposition. Improvement of the TOC-degradation performance by Cu2+-NaY [OA] was tentatively attributed to the removal of sodium and possibly aluminium in the zeolite.