Sr2−xCaxMgTeO6 (0 ≤ x ≤ 2) ceramics were prepared by the solid-state ceramic route. Structure and microstructure of the compounds were investigated using XRD, TEM, and SEM methods. The system undergoes a transition from pseudocubic tetragonal I4/m symmetry for x = 0 (Sr2MgTeO6) to pseudotetragonal monoclinic P21/n symmetry for x > 0. The dielectric properties of the ceramics were studied by the resonance method. The temperature coefficient of resonant frequency is negative throughout the series; permittivities were in the range 13.2−14.3, and quality factors varied from 27500 to 81000 (5−6 GHz).