Surface treatment by means of fibre laser radiation using various processing gas compositions was conducted on cold isostatic pressed (CIP) Si3N4 and ZrO2 engineering ceramics to observe changes in their surface integrity, chemical composition and distribution of the heat affected zone (HAZ). The as received and fibre laser treated surface topography was measured in 3D using white-light interferometry (WLI). Scanning electron microscopy (SEM) was then used to observe the microstructural integrity prior to and after the fibre laser treatment. Energy dispersive X-ray (EDX) was employed thereafter to detect the change in the chemical composition. Surface melting and distribution of the melt zone was found with all treated samples of Si3N4 and ZrO2. The surface finish and the material removal varied with using the various gas compositions. Fibre laser processing with N2 on Si3N4 proved to be the most influential in effecting morphology changes, whilst Ar with ZrO2 ceramics in order to locally melt and redistribute the top layer of ZrO 2 ceramics, producing a better bondage of the grain boundaries. However, the maximum materials removal was found with using O2 gas with both ceramics particularly with Si3N4 as the surface profile of the treated zone was completely modified. Effect of oxidation occurred with all samples but was less for ZrO2 ceramics in comparison with that of the Si3N4.