We present a theoretical investigation about structural parameters, electronic properties, and vibrational modes of dihydrogen-bonded (DHB) complexes formed by BeH2···HX with X = F, Cl, CN, and CCH. From B3LYP/6–311++G(3d,3p) calculations, it was verified that some important molecular changes in the free monomers upon the formation of the complexes, in which we can mention the elongation in both BeH2 and HX molecules, description of the bathochromic effect assigned at the monoprotic acids, as well as tendency in the dihydrogen bond strength. Thus, a suitable explanation about these phenomena was performed through the calculations of the Bader’s atoms in molecules (AIM) theory, which described the charge transfer between the HOMO orbital of the beryllium hydride and the LUMO orbital of the HX species.