A complete assignment of the Raman active modes of 1,10-phenanthroline-5,6-dione in the 100−4000 cm-1spectral region is reported. Intense well resolved spectra of solid phendione with high S/N are reported.Assignment of the normal modes with appropriate symmetry representation symbols was achieved by employingdensity functional theory calculations. Our calculations were modeled on results previously reported forphenanthroline. Results of the B3LYP calculations were consistent and established that phendione possesssixty fundamentals.