Previous empirical assignments of the normal modes of Ru(η5-C5H5)2 were checked against the results of a calculation applying density functional theory (DFT). After some reassignments, following those recently suggested for Fe(η5-C5H5)2 (after theoretical model calculations), a satisfactory agreement was observed.Recently communicated polarized Raman spectra of an oriented Ru(η5-C5Me5)2 single crystal were used here for the identification of the irreducible representations of a number of Raman active normal modes (assuming molecular D5h symmetry) which agree well with the results of the DFT calculation. The energies of IR active fundamental vibrations, extracted from recently communicated FIR/MIR spectra (pellets), were correlated with comparable energies of IR allowed irreducible representations of the DFT calculation and assigned. Both the skeletal and the intra-ligand normal modes could be correlated with the idealized standard motions (νis) of the model sandwich complex Ru(C5C5)2, and previous assignments had to be revised. Neglecting the νCH vibrations (which are off by ca. 50 cm−1) an r.m.s. deviation of 9.8 cm−1 (for 47 assignments) of the remaining normal modes could be achieved.Graphical abstractHighlights► DFT calculations on normal modes of an organometallic sandwich complex. ► Polarized single crystal Raman spectra of an organometallic sandwich complex. ► Excellent agreement of experimental spectra and DFT predictions.