Abstract This study examined the release of toxic metal ions from, and the cell response to, a cobalt–chromium (Co–Cr) alloy fabricated using either traditional casting or selective laser melting (SLM) techniques. The releases of Co, Cr, and Molybdenum (Mo) were examined using inductively coupled plasma mass spectroscopy (ICP-AES) for specimens immersed in artificial saliva solution at 37°C for 7 days. Cell response to samples was evaluated by investigating the morphology of mouse 3T3 fibroblasts. Cell proliferation was assessed using an MTT assay. The cell culture medium exposed to specimens was also tested for metal ion release using ICP-AES. Concentrations of Co and Mo were significantly lower in the SLM group in comparison with the traditional casting group. Cells exposed to both SLM and traditional cast samples showed normal cell morphology; however, cell proliferation on SLM samples was higher. In conclusion, the ion release of Co–Cr alloy prepared by selective laser melting was lower and showed better biocompatibility than samples prepared by a traditional casting technique.