Thioamide substitution of backbone peptide bonds can probe interactions along the main chain of proteins. Despite theoretical predictions of the enhanced hydrogen bonding propensities of thioamides, previous studies often do not consider the geometric constraints imposed by folded peptide secondary structure. This work addresses drawbacks in previous studies that ignored the geometry dependence and local dielectric properties of thioamide hydrogen bonding and identifies cases where thioamides may be either stronger or weaker hydrogen-bonding partners than amides.