Purpose: This study was carried out to compare the effect of laser surface treatment on cubic and tetragonal zirconia ceramics regarding; phase transformation tetragonal-monoclinic (T-M), surface topography, mechanical properties and biaxial flexural strength before and after low thermal degradation (LTD) aging. Materials and Methods: sixty discs (N=60) of CAD/CAM zirconia were used in this study. These specimens were divided into two main groups according to type of zirconia. Group I: (n=30) Cubic Zirconia (DD cubeX2), while Group II: (n=30) Tetragonal zirconia (Superfect-Zir). Then each group further subdivided into two subgroups according to surface treatment, subgroup (1): control without surface treatment, subgroup (2): laser surface treatment .Specimens form each subgroups were tested for the following; Phase transformation, surface topography, and mechanical properties before and after Low Thermal Degradation (LTD) aging test. Results: Statistical analysis revealed that there was a statistical significant difference between the two tested groups regarding the surface topography, biaxial flexural strength, and surface hardness. Also there was a statistical significant difference regarding the surface treatment and before/after LTD and laser among the tested zirconia ceramics. Conclusions: laser surface treatment improved the properties of tetragonal / cubic zirconia, and increases their resistance to low thermal degradation LTD aging.