This article discusses the microstructure and mechanical properties of an Al-3.0Ce-0.9Ca-1.9Mn-1.2Zr alloy produced by selective laser melting (SLM) technology. The new alloy leverages the excellent heat resistance of Al-Ce alloys, incorporating Ca to lower both the cost and density, while the addition of Mn and Zr enhances formability and provides additional precipitation strengthening. Through the optimization of heat-treatment parameters, the optimal conditions were determined, with an annealing temperature of 375 °C and a holding time of 8 h. After annealing, the alloy’s tensile strength increased from 333 MPa to 412 MPa, yield strength rose from 246 MPa to 359 MPa, and elongation decreased from 24.4% to 16.4%. Compared to the as-built state, tensile strength and yield strength increased by 23.6% and 46.1%, respectively, while elongation decreased by 32.7%. The alloy demonstrates excellent heat resistance, with yield strengths at test temperatures of 200 °C, 250 °C, 300 °C, and 350 °C at 167 ± 17 MPa, 144 ± 8 MPa, 84 ± 4 MPa, and 57 ± 5 MPa, respectively. Notably, alloying imparts a degree of superplasticity, likely due to the synergistic effects of the Ca, Mn, and Zr elements.