Al-Ce-based alloys, characterized by low density, excellent coarsening resistance and good castability, are promising materials for stable service in the temperature range of 200~450 ℃ .In this study, an alloy with a nominal composition of Al-10Ce-5Ni-4Cu (wt.%, named ACNC) was prepared. The microstructure evolution in the as-cast sample and during isothermal aging was systematically investigated, and its tensile properties at room and elevated temperatures were tested, along with the underlying strengthening mechanisms. The results indicate that the ACNC alloy has a hypoeutectic microstructure, consisting of primary α-Al dendrites, “rod-like or plum-blossom-like” Al3Ni phases, “fishbone-like” Al11(Ce, Cu)3 phases, and eutectic colonies. Within the eutectic colonies, the Al3CeCu and Al3Ni phases are entangled in a fibrous manner. After isothermal aging at 450 ℃ for 24 h, the width of the eutectic phases increase from (154±64) nm to (519±241) nm, and the eutectic spacing expandes from (380±155) nm to (1 029±511) nm, accompanied by aprogressive decrease in hardness. In contrast, severe overaging at 590 ℃ for 5 h leads to rapid spheroidization of the Al3Ni and Al3CeCu phases, resulting in a sharp decrease in hardness. The yield strengths of the alloy at room temperature, 200, 300 and 400 ℃ are measured as (136±7) MPa, (121±2) MPa, (86±1) MPa, and (45±2) MPa, respectively.