In the crystal structure of the title compound, [Co(C12H8N2)3](BF4)2·CH3CN, the molecular packing involves dimers of distorted octahedrally coordinated cations which are held together by one π–π [centroid–centroid = 3.542 (4) Å] and two C—H⋯π interactions [2.573 (4) Å] resulting in a P4AE (Parallel Fourfold Aryl Embrace) motif. The anions are found in aryl boxes formed from the phenanthroline ligands