Living bacteria (Rhodococcus ruber) and yeast (Saccharomyces cerevisiae) cells can be embedded within magnesium phosphate cement (MPC). The cements are prepared by the admixture of microorganisms to a water-based slurry system of Mg3(PO4)2 powder and ammonium phosphate solution whereas the setting of the slurry occurs within few minutes. To test the biocatalytic activity of the embedded microorganisms the phenol degradation by R. ruber and the glucose conversion by S. cerevisiae are described. Embedded cells survived within the cements and remain active. However, the glucose or phenol consumption rate was clearly reduced after immobilization within the compact macroporous concrete matrix. By using leachable pore forming additives or by admixture of cellulose fibers the macroporous structure of the MPC can be improved. The bioactive composite material exhibits good mechanical and chemical stability. It can be used as new stable biocatalysts, e.g., for applications in bioremediation and biotechnology.