To improve the condensed-phase reaction rate of ε-CL-20, polydopamine (PDA)-nickel complex-coated multiwalled carbon nanotubes (CNTs) have been prepared and used as combustion catalysts. The PDA-Ni complex has been prepared and in situ coprecipitated with ε-CL-20 by an antisolvent crystallization process in its dimethyl sulfoxide (DMSO) solution. It has been shown that crystalline CL-20 composites included with PDA-Ni complexes are polygon-shaped with a smooth surface and an average diameter of 10-15 μm, whereas it is 140 μm for raw ε-CL-20 crystals. The catalytic reactivity of the complex on thermolysis of CL-20 has been investigated using the differential scanning calorimetry (DSC) and thermogravimetry (TG)-coupled Fourier transform infrared (FT-IR) spectroscopy technique. It has been found that CNT@PDA-Ni complexes have catalytic effects on the decomposition of ε-CL-20 by decreasing/shifting of the exothermic peak from T p = 240.1 to 238.7 °C. The FT-IR spectra of CL-20 decomposition products under the effect of the catalyst predominantly show peaks at 1274, 1644 and 1596, 1912, 2265, and 1956-1800 cm-1, indicating the presence of fragments with N2O, NO2, NO, HNCO, and NO/CO, respectively. The change in the ε-CL-20 decomposition mechanism should be attributed to the catalytic action of CNT, decreasing the formation of NO2. Also, under the effect of the carbon-based catalyst, the HNCO formation was detected at another temperature in comparison with raw CL-20, with peak absorption at 224.1 vs 232.3 °C and the evolution was completed at 250.8 vs 246.2 °C, respectively.