An ultrafast nonlinear coherent laser spectroscopy termed vibrational sum-frequency generation (SFG) was used to monitor vibrational transitions of a self-assembled monolayer (SAM) of 4-nitrobenzenethiolate (NBT) on Au after Au flash heating. Ultrafast thermoreflectance measurements showed the surface temperature jumps Delta T were in the 35-250 K range. The NBT symmetric and antisymmetric nitro stretches nu sNO2 and nu asNO2 and a phenyl ring stretch nu CC were probed. Flash heating caused these transitions to lose intensity, shift, and broaden. The time dependences all had overshoot-decay-plateau structures. In the long-lived plateau, the SAM was in thermal equilibrium with the hot Au surface. The SFG plateau intensity losses of nu sNO2 and nu CC, two vibrations with parallel transition moments, were identical, indicating that the SFG intensity loss was caused by thermally induced SAM orientational disorder. The T-jump-induced frequency shifts of nu sNO2 and nu asNO2 were identical and opposite in sign. The rise times of the shifts were identical and equal to the similar to 3.5 ps time constant for the rise of Au surface temperature, which indicates that both shifts were caused by anharmonic coupling to the same lower-energy vibration. The temperature dependence of the nu sNO2 shift and width indicated that this vibration was the similar to 480 cm(-1) nitro bend. The nu sNO2 temperature dependence was interpreted using a vibrational energy exchange mechanism between the nitro stretch and bend.