The cis-trans isomerization of N-acetylproline methylamide has been investigated by density functional theory. The introduction of an electron-withdrawing group at the C-gamma of proline has notable geometrical and energetic consequences on the cis-trans isomerization. In the presence of the fluoro and hydroxy substituents, the preferred mode of rotation of the acetyl group is in a counterclockwise direction, assisting in the formation of an N-HN intramolecular hydrogen bond in the transition structures and enhancing the pyramidalization of, the prolyl nitrogen. This study illustrates the important role the intramolecular N-HN hydrogen bond plays in the cis-trans isomerization. of proline-containing molecules and the catalytic possibilities of hydrogen bonding.