A comparative study between the fiber and an Nd:YAG laser during the surface treatment of a Si3N4 engineering ceramic was conducted to investigate the contribution of the laser-beam brightness. A fiber and an Nd:YAG laser with identical process parameters were employed. The effects of the laser-beam brightness were investigated with respect to modification in the dimensional size and the microstructure of the laser irradiated Si3N4 engineering ceramic. The results showed a change in the dimensional size and the microstructure of the surfaces treated by the two lasers despite using identical laser processing parameters. This was due to the difference between the laser-beam brightness of the two lasers as the fiber laser produced larger power per unit area in Steradians when compared to the Nd:YAG laser. Owing to this, high interaction temperature, larger fibre laser–ceramic interaction zone and melt-pool at the laser–Si3N4 interface were found, which further led to changes in the physical attributes of the Si3N4 engineering ceramic. This shows that laser surface treatment using high brightness would be cost effective as the brighter laser utilises lower power for the same surface treatment in comparison with that of a low brightness laser. Therefore, processing ceramics and other materials by employing high brightness lasers could aid in gaining an economical benefit.