Molecular dynamics simulations are used to obtain potentials of mean force for pairs of neopentane molecules immersed in aqueous solutions containing urea, trimethylamine-N-oxide (TMAO), or both solutes at once. It is shown that the hydrophobic attraction acting between neopentane pairs in pure water and in water-urea solution is completely destroyed by the addition of TMAO. This strongly suggests that TMAO does not counter the protein denaturing effect of urea by enhancing hydrophobic attraction amongst nonpolar groups.