The flexible lattice of hydroxyapatite (HAP) allows for doping with ions widely varying in size and charge and these ions can impart a range of properties that could be harnessed for high technology applications. However, incorporation of combinations of ions, each of which endows HAP with different properties, has rarely been explored, let alone in combination with polymers. Carbonated hydroxyapatite (CHAP) dually doped with magnesium and selenite ions (Mg– Se–CHAP) was synthesized at different contents of the Mg 2? dopant and inte- grated within electrospun e-polycaprolactone (PCL) microfibers. The formula Mg x Ca ðÞ PO 10xðÞ 4 5:8 ðÞ SeO 2 0:2 OHðÞ represented the ceramic component of Mg– Se–CHAP/PCL fibers, whose properties were studied for different values of the 2 stoichiometric parameter x in the 0.0 B x B 0.5 range. The structural investigation indicated that the lattice parameter a decreased with the addition of Mg from x =0tox = 0.3, at which point it reached its minimal value of 9.414 A ˚ , while the lattice parameter c increased with the addition of Mg 2? from x =0to x = 0.3, at which point it reached its maximal value of 7.050 A logical properties depended strongly on the Mg 2? ˚ . The morpho- content, as the fibrous scaffolds became more networked, rougher on the surface, and less porous with the addition of Mg 2? . All of these surface properties affected the human fibroblastic HFB4 cell response to these materials. While the cell viability tests indicated a 2?