Various compositions of Li1-2xCaxSi2N3 (x = 0–0.2) were synthesized by the reaction of Li3N, Si3N4, and Ca3N2 at temperatures of 1873–2073 K. Ca was incorporated into the LiSi2N3 host lattice to form a solid solution of Li1-2xCaxSi2N3. The activation energy for ionic conduction was decreased and ionic conductivity at room temperature was enhanced by Ca doping. At 298 K, the ionic conductivity of densified Li1-2xCaxSi2N3 (x = 0.075) ceramic reached 1.6 × 10−5 S m−1, almost four orders of magnitude higher than that of densified Li1-2xCaxSi2N3 (x = 0) ceramic (3.1 × 10−9 S m−1). The change in the LiSi2N3 framework upon Ca doping decreased the interaction between the ions and increased the number of defects in the structure, making it easier for mobile Li+ ions to migrate. Moreover, the incorporation of aliovalent substitutional Ca2+ ions in the LiSi2N3 lattice is expected to create Li+ vacancies (VLi) for charge compensation (Li1-2xCaxVLiSi2N3), thereby increasing the number of mobile Li+ ions.