In this paper, we systematically studied the mechanical and electronic properties of a series of antiperovskite-type Ti-based ternary carbides and nitrides AXTi3 (A = Ba, Ca, In, Sn, Sr, Zn, Cu, Al, Ga, Cd, and La; X = C, N) from first-principles calculations. By calculating the formation energies, elastic constants, and other mechanical parameters, we predicted that 7 carbides ACTi3 and 7 nitrides ANTi3compounds are stable among the 22 compounds. The predicted large Young's modulus and high hardness imply a good mechanical application prospect of AXTi3. Particularly, SnNTi3 was found to show ferromagnetic ground state. For the electronic structure, our results confirm that the compounds are metallic in nature, and the density of states near the Fermi energy is predominately contributed by Ti-3d states. The effect of A- and X-site atom doping on AXTi3 can be evaluated by rigid band approximation. Our prediction will be useful for the experimental exploration of the new antiperovskite compounds.