Carbon–palladium composites have been investigated by the method of transmission electron microscopy. The composites have been obtained by two different processes: physical vapor deposition (PVD) and chemical vapor deposition (CVD). The relation between the average size of a palladium particle, the time, and temperature has been carried out. The samples were annealed at different temperatures—from $$500\,^{\circ }\hbox {C}$$ 500 ∘ C to $$750\,^{\circ }\hbox {C}$$ 750 ∘ C but also for three different times, that is, 5 min, 10 min, and 30 min. Activation energies were calculated from the Arrhenius equation. Obtained values for PVD and PVD/CVD samples are: $$64.6\,\hbox {kJ}{\cdot }\hbox {mol}^{-1}$$ 64.6 kJ · mol - 1 and $$38.8\,\hbox {kJ}{\cdot }\hbox {mol}^{-1}$$ 38.8 kJ · mol - 1 , respectively. Determination of the activation energy will be useful in controlling the growth of palladium grains. Significant differences in values for both series resulted from encapsulation in graphite–palladium particles, which were obtained in the PVD/CVD process. Those graphite planes are formed at temperatures above $$600\,\,^{\circ }\hbox {C}$$ 600 ∘ C and significantly slow down the growth of palladium particles.