Using the picosecond visible light at 532.1 nm and infrared light at 2800-3100 cm(-1), we observed the interference between the intramolecular IR-visible and visible-IR processes in the doubly resonant sum frequency generation vibrational spectroscopy of Rhodamine 6G adsorbed at the air/water interface. The interference phenomenon exists for both the C-H stretching vibrations in the 2800-3100 cm(-1) region and the skeleton vibrations in the 1450-1700 cm(-1) region. The relative strength of the visible-IR process at different wavelengths is the result of the electronic structure of the molecule. This is the first direct observation of the visible-IR sum frequency generation process in the electronically excited state of a model molecular system.