Laser melting and re-solidification has been used to densify and homogenize ceramic surfaces, leading to increased high-temperature corrosion and erosion resistance. Although complete sealing of pores can be achieved on the surface, pores have been observed in the boundary between the laser-treated zone and the untreated bulk. This paper investigates the mechanisms of pore formation and the various factors affecting it. A simple analytical model that predicts the maximum final pore diameter and location along the treated zone/untreated bulk boundary is derived, in terms of the materials properties and the processing parameters. Experimental investigations for a range of processing speeds and power densities have verified the model predictions, identifying the effects of processing speed and laser power density on the maximum pore diameter.