The reaction mechanism for the formation of the pseudo-silaazatriene 1 by the reaction of 1 equivalent of bis-silylene with 3 equivalents of azide Me3SiN3 has been explored at M06/def2-TZVPP//BP86-D3(BJ)/def2-TZVPP level of theory. The reaction mechanism is guided by the high Lewis basicity of the silicon lone pair and the high Lewis acidic character of Si-N bonds, as well as by the high tendency to eliminate N2 from Me3SiN3. The first step of the reaction is the formation of [3+1] cycloaddition product (I1) by the synergetic interactions of the lone pair on the silylene silicon with the π* molecular orbital of Me3SiN3 which is majorly localized on the terminal nitrogen atom, and the donation of the σ-type lone pair on the nitrogen atom connected to the SiMe3 group with the Si-N σ* orbital on silylene. The elimination of N2 from I1 results in the formation of pseudo-silaimine intermediate I2 having a dicoordinated, monovalent nitrogen atom. The Si-Si bond cleavage of I2 results in intermediate I3, which is susceptible to [3+1] cycloaddition reaction with two molecules of Me3SiN3 in a stepwise manner results in I7 having two silaimine and one silaamine moieties. Further 1,3-silyl migration results in pseudo-silaazatriene 1.