Many curcuminoid derivatives have been reported to have multiple biological activities. The aim of this study was to improve the biological activity of curcuminoids by synthesizing 16 new derivatives which combined cinnamic acids with curcuminoids, and we also analyzed the structure–activity relationship of the new compounds. Almost all the new compounds showed encouraging activity, especially compound 7g. It had much better antioxidant activity than curcuminoids and Vitamin C (VC), and also had the most significant antibacterial activity, which was 5-folder better than ampicillin (one of the best marketed antibiotics) with a minimum inhibitory concentration (MIC) of 0.5 µg/mL against Gram-positive cocci (Staphylococcus aureus and Streptococcus viridans) as well as Escherichia coli and 0.6 µg/mL against Enterobacter cloacae. Compound 7g also showed the greatest anticancer activity with a much lower IC₅₀, which was 0.51 µM against MCF-7, 0.58 µM against HepG-2, 0.63 µM against LX-2, and 0.79 µM against 3T3. The results suggest that these compounds have promising potential as candidates for the treatment of cancer and thus further studies are warranted.