The title compound, [Co(C10H9O3)(C12H8N2)2(H2O)]NO3 (I), crystallizes in the triclinic space group P with a monomeric [Co(3-meo-cin)(phen)2(H2O)]+ cation and a nitrate anion (3-meo-cin = 3-meth-oxy cinnamic acid) in the asymmetric unit. The CoII ion is coordinated by four N atoms from two 1,10-phenanthroline ligands and two O atoms, the first from a meth-oxy cinnamate ligand and the second from a coordinated water mol-ecule, forming a distorted octa-hedral geometry. Discrete entities of the cation and nitrate anion are formed by water-nitrate O-H⋯O and phen-nitrate C-H⋯O hydrogen bonds. The components are further assembled into chains along the c-axis direction. Layers are than formed by slipped π-π stacking inter-actions parallel to the bc plane. The inter-molecular inter-actions in the crystal structure were qu-anti-fied and analysed using Hirshfeld surface analysis.