Vibrational spectra of di-2-pyridyl ketone and di-2-pyridyl ketone-18O have been recorded in the solid and molten state in the infrared (4000–100 cm−1) and the Raman (4000–50 cm−1). Polarized Raman spectra of the molten state have also been measured. The assignment of vibrational bands is performed using the group vibrational concept, isotipic shifts data and polarization features of the normal modes. The presence of symmetric and antisymmetric vibrations arising from the coupling of both pyridyl rings is found and discussed.