In the present paper we report the formation of CNx phases during mechanical treatment of graphite in a nitrogen atmosphere. Samples containing approximately 25 wt.% of CNx phases have been obtained with the experimental conditions presented in this work. The formation of carbon–nitrogen bonds has been proved by infrared (IR) and X-ray photoelectron spectroscopy (XPS). In addition, thermogravimetric analysis (TGA) shows that the mechanosynthesized CNx materials decompose to molecular nitrogen at temperatures above 873 K.