A biodegradable magnesium (Mg) scaffold as bone repair material is desired to demonstrate antibacterial function to reduce the risk of bacterial infection. In this work, mesoporous bioactive glass (MBG) was used as a carrier of copper (Cu) ions to obtain Cu-doped MBG (Cu-MBG), which was then incorporated into a Mg-based scaffold fabricated by laser additive manufacturing. Results showed that Cu-MBG endowed the Mg-based scaffold with favorable antibacterial activity, with an antibacterial rate of 81% (against E. coli), owing to the sustained release of Cu²⁺ ions from Cu-MBG. More significantly, Cu-MBG with excellent bioactivity effectively induced the in situ deposition of the apatite product, which served as a protective layer and consequently reduced the degradation rate of the Mg matrix. Furthermore, Cu-MBG improved the cell response, including cell growth and adhesion. This study proposed a new strategy to simultaneously improve the antibacterial activity, degradation behavior and cell response of the biomedical Mg-based material.