In this paper, Mg-substituted TCP, with the general formula (Ca1−xMgx)3(PO4)2 and 0.01 ≤ x ≤ 0.045, were produced by wet chemical synthesis from Ca(OH)2, H3PO4 and MgO, after calcinations at three different temperatures between 750 and 1050 °C. The influence of different amounts of Mg substitution on the physical properties, microstructure, and sintering behavior of calcium phosphate powders was evaluated. Thermal analytical techniques, together with X-ray diffraction analysis, were successfully combined in order to characterize the occurring phase transformations during annealing of the powders. The results show that the addition of small amounts of Mg (up to 1.5 mol % ) are adequate to postpone the β–α TCP phase transformation to 1330 °C and to accelerate the densification process during sintering of β-TCP ceramics.