Hot pressing is one of the promising routes for graphitization of carbon materials. In the present work, high-pressure high-temperature behaviour of 13C-enriched fine-grained graphitic material has been studied by using a set of experimental tools such as scanning electron microscopy, Raman scattering, X-ray diffraction, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopies, and solid-state nuclear magnetic resonance (NMR) spectroscopy. The material has been annealed at a temperature of 1200 or 1500 °C using a stabilizing pressure of 5 GPa. It shown, that addition of small amount of water during the annealing at 1200 °C results in a better local atomic ordering of carbon material and increases the hydrocarbon fraction. Well-ordered graphite crystals enriched with 13C isotope are formed on the surface of nickel ampule at 1500 °C. An increase in processing time from 2 to 15 h decreases the defect density and improves the graphitization level of the material.