The nicotinamide adenine dinucleotide coenzymes [NAD(P)(H)] are strong redox agents naturally present in wheat flour, and are indispensable cofactors in many redox reactions. Hence, it is not inconceivable that they affect gluten cross-linking during breadmaking. We investigated the effect of increasing concentrations of NAD(P)(H) on gluten cross-linking, dough properties, and bread volume using two flours of different breadmaking quality. Separate addition of the four nicotinamide coenzymes did not significantly affect mixograph properties. While addition of NAD(+) hardly affected bread volume, supplementation with NADP(H) and NADH significantly decreased loaf volumes of breads made using flour of high breadmaking quality. Wheat flour incubation with NAD(P)H under anaerobic conditions increased wheat flour thiol content. while NAD(P)(+) increased the extractability in SDS-containing medium of the protein of the strong breadmaking flour. Based on the results, it was hypothesized that at least three reactions, competing for NAD(P)(H), occur during breadmaking that determine the final effect on protein, dough, and loaf properties. Next to coenzyme hydrolysis, the experiments pointed to coenzyme oxidation and NAD(P)(H) dependent redox reactions affecting protein properties.