This article reports the successful one-step synthesis of two micron-sized composite powders consisting of chitosan and amorphous calcium phosphate. These composite materials are prepared by spray drying of a solution containing chitosan and calcium phosphate precursors. The co-precipitation of chitosan and calcium phosphate precursors during the process induces a highly homogeneous distribution of the phases. The mineral phase identified as spherical nanoparticles dispersed in chitosan showed no chemical bonding with the polymer. As demonstrated by electron microscopy, small angle X-ray scattering and spectroscopies, variation in chitosan concentrations significantly influences the size and spatial distribution of the mineral phase. These results present a promising approach for the preparation of chitosan/amorphous calcium phosphate composite powders with controlled and tunable properties with potential applications in the field of biomaterial engineering such as bone substitutes.