In the present study, the assembly of 6-aminonicotinic acid with inorganic acids (HBr, HNO3 and H3PO4) has been performed, which resulted in the molecular salts C6H7N2O2+·Br− (1), C6H7N2O2+·NO3− (2) and C6H7N2O2+·H2PO4− (3), respectively. These three molecular salts have been characterized by single-crystal X-ray diffraction, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and UV–Vis absorption spectroscopy (UV). The results revealed that molecular salt 1 exhibits an infinite 1-D chain structure stabilized mainly by N–H⋯Br contacts, while 2 and 3 show a 2-D network and a 3-D stereoscopic framework, respectively, which are stabilized mainly by strong N–H⋯O hydrogen bonding contacts. Hirshfeld surface analysis demonstrated the presence of H⋯H, O–H⋯N, C–H⋯π and π⋯π intermolecular interactions. In addition, the UV–Vis spectra exhibit a slight blue-shift to a shorter wavelength, which suggests the clear influence of the inorganic anions.