Nitromethane-d3 is a deuterated derivative of nitromethane. Its pyrolytic decomposition in the absence and presence of nitrogen dioxide have been studied. Molecular structure studies suggest that its molecule is composed of a highly asymetrical top consisting of a heavy planar frame of NO2 (C2v symmetry) and a lighter top of CD3 (C3v symmetry). Rotational constants, high-resolution Fourier transform infrared (FTIR) spectrum and DFT (Density Functional Theory) calculations of nitromethane-d3 have been evaluated. Various physicochemical properties (densities, viscosities, speed of sound and refractive indices) of CD3NO2 have been evaluated in the temperature range of 293K to 308K.