Abstract: The aim of this study was to evaluate the antibacterial properties of oyster, hard clam, and sea urchin shell powders as a result of calcination. After subjection to calcination at 1050 °C for 2 h, and as identified by FTIR and XRD spectra, the structures of oyster, hard clam, and sea urchin shell powders were mainly transformed into calcium oxide, with slight amounts of calcium hydroxide. Metal content testing revealed no detectable harmful heavy metals, and showed rich content of trace elements including Ba, Sr, Mg, and Mn. To evaluate their antibacterial properties, activity against five foodborne microorganisms was assessed using the disk diffusion method, which indicated the presence of antibacterial activity in these products at a concentration of 1 %. These results indicate antibacterial potential for oyster, hard clam, and sea urchin shell powders after subjection to calcination.