High pressure processing (HPP) can inactivate pathogenic microorganisms and degradative enzymes without the use of heat, thereby minimizing the destruction of flavors, nutrients, and other quality attributes. Lipoxygenase plays a role in the off flavor production of tomatoes, while pectinesterase and polygalacturonase impact tomato texture. The purpose of this study was to determine HPP’s ability to inactivate lipoxygenase, pectinesterase, and polygalacturonase in diced tomatoes. Processing conditions used were 400, 600, and 800 MPa for 1,3, and 5 minutes at 25°C and 45°C. The magnitude of applied pressure had a significant effect on inactivating lipoxygenase and polygalacturonase (p<0.05), and complete loss of activity occurred at 800 MPa. Pectin esterase was very resistant to pressure treatment, and certain pressure-time-temperature combinations produced activation of the enzyme. Percent soluble solids, pH, titratable acidity, and a/b values did not change significantly in the high pressure processed samples as compared to the control, but L values increased. Titratable acidity and pH were found to change, however, when comparing between different pressure treatments.