The vibrational energy relaxation of 9-fluorenone and its complex with alcohols has been investigated by sub-picosecond pump-probe spectroscopy. The infrared absorption spectrum of 9-fluorenone in alcohol shows three distinct contributions from the free 9-fluorenone, its complex with one alcohol molecule, and that with two molecules. The time constant of the vibrational energy relaxation of the free 9-fluorenone is 4.7 +/- 0.1 ps, and that of the 1:1 complex is 2.3 +/-0.1 ps. The acceleration of the vibrational energy relaxation due to hydrogen-bond formation is discussed in terms of the Fermi golden rule. (C) 2007 Elsevier B.V. All rights reserved.