trans-Cinnamaldehyde is a major component of Cinnamomum cassia and has been reported to give rise to antimicrobial properties in cinnamon spice. In order to better understand the relationship between the structure of trans-cinnamaldehyde and its antimicrobial role, fifteen structurally different trans-cinnamaldehyde derivatives were selected for study based on their predicted electrophilicities. Both synthesized and commercial trans-cinnamaldehyde derivatives were evaluated for their antibacterial activity, with modest mM activity levels found against both E. coli and S. aureus. An initial mechanism of action study, suggesting that the electrophilicity of the trans-cinnamaldehydes affects the antibacterial activity, was conducted as well as an exploration of their ability to alter bacterial cell wall integrity. In addition, in vivo toxicity levels were determined using the larvae of the greater wax moth, Galleria mellonella, with all derivatives tested showing low toxicity.