In the title compound, C(11)H(9)N(5)O, the pyrazolo-pyrimidin-4-one ring system is almost planar, with a maximum deviation of 0.0546 (13) Å for the O atom. The crystal packing is stabilized by inter-molecular N-H⋯N, C-H⋯O and C-H⋯N hydrogen bonds. In addition, π-π stacking is found between the pyridine ring and the pyrazolo-pyrimidin-4-one ring systems, with centroid-centroid distances in the range 3.9627 (12)-4.6781 (12) Å.