2,4-Dinitrodiphenylamine (DNDPA) has been studied as regards its crystal structure and thermal decomposition characteristics using X-ray diffraction (XRD), simultaneous thermal analysis, ultraviolet and Visible spectroscopy, infrared spectroscopy, hot-stage microscopy and high performance liquid chromatography (HPLC). The elementary cell parameters obtained from the XRD pattern are a=17.002 Angstrom, b = 17.002 Angstrom, c = 20.400 Angstrom. The crystal structure belongs to the hexagonal system with c/a ratio 1.1999. IR spectra of 2,4-DNDPA have also been recorded and the bands assigned. Kinetics of thermolysis has been followed both by isothermal thermogravimetry (TG) and HPLC. The best linearity with a correlation coefficient of 0.994 was obtained for the two-dimensional diffusion controlled equation in TG. Activation energy was found to be 83.0 kJ/mol and log A (in s(-1) = 6.0 from isothermal TG. The rupture of the C-NH bond followed by the C-NO2 bond constitutes the primary step in the thermolysis and the decomposition is free-radical assisted.