In this paper, we present the results of processing metallic gallium in an ammonia vapor medium at 2 bar pressure by femtosecond laser pulses. The influence of the ammonia concentration and the mode of laser beam scanning on the result of laser action is considered. It has been established that an increase in the concentration of ammonia vapor and a change in the scanning regime lead to a radical change in the laser ablation process. A decrease in the scanning speed leads to the cessation of the ablation process and the development of the nitridation process of the gallium surface, accompanied by the formation of columnar structures up to 12 mm long and about 100 μm in diameter. The synthesized nanoparticles and structures were studied using scanning electron microscopy, Raman spectroscopy, and X-ray analysis.