The structural, bonding and elastic properties of alkali amidoboranes (LiNH2 BH3, LiNH3 BH4, and NaNH2 BH3) have been studied. We employ first principles calculations based on van der Waals (vdW) corrected density functional theory. In the presence of alkali metal the electronic distributions of B–H and N–H bonds are modified and reduce the di-hydrogen bonding. These effects significantly reduce the role of vdW in binding these compounds. Further, the band structure and density of states are calculated to get basic insights on distribution of electronic states. These compounds are found to be wide band gap insulators with the band gap values for LiNH2 BH3, LiNH3 BH4, and NaNH2 BH3 are 4.08, 5.61, and 3.96 eV, respectively. The charge density distribution and bond population analysis are used to understand the nature of bonding. It is noted that these compounds have a strong covalent bonding between B–H and N–H atoms. The calculated elastic constants reveals that these compounds are mechanically stable and LiNH2 BH3 is found to be less plastic compared to the LiNH3 BH4 and NaNH2 BH3.