The molecular structure of 7-amino-2-methylsulfanyl-1,2,4- triazolo[1,5-a]pyrimidine-6-carboxylic acid is reported in two crystal environments, viz. as the dimethylformamide (DMF) monosolvate, C7H7N5O2S C3H7NO, (I), and as the monohydrate, C7H7N5O2S H2O, (II), both at 293 (2) K. The triazolo- [1,5-a]pyrimidine molecule is of interest with respect to the possible biological activity of its coordination compounds. While the DMF solvate exhibits a layered structural arrangement through N...O hydrogen-bonding interactions, the monohydrate displays a network of intermolecular O...O and N...O hydrogen bonds assisted by cocrystallized water molecules and weak π–π stacking interactions, leading to a different three-dimensional supramolecular architecture. Based on results from topological analyses of the electrondensity distribution in X—H...O (X = O, N and C) regions, hydrogen-bonding energies have been estimated from structural information only, enabling the characterization of hydrogen-bond graph energies.