This study examined the inhibitory effects of trans-cinnamaldehyde (CA), an aromatic aldehyde derived from Cinnamomi Cortex, on Saccharomyces cerevisiae cell wall synthesizing enzymes in vitro. This compound was found to be a noncompetitive inhibitor of beta-(1,3)-glucan synthase and a mixed inhibitor of chitin synthase 1 with 50% inhibitory concentrations (IC50) of 0.84 and 1.44 mM, respectively. Chitin synthases 2 and 3 were less sensitive than chitin synthase 1 to CA. CA can be useful as a model compound of cell wall inhibitors for the development of effective antifungal agents.