In the title compound, C6H10N3(+)·Cl(-), the cation is essentially planar with an r.m.s. deviations of the fitted atoms of 0.008 Å. In the crystal, adjacent ions are linked by weak N-H⋯Cl hydrogen bonds involving the pyrimidine and amine N atoms, forming a three-dimensional network. C-H⋯π inter-actions between the methyl and pyrimidine groups and π-π stacking [centroid-centroid distance = 3.474 (1) Å] between parallel pyrimidine ring systems are also observed.