In this study, the microstructure and mechanical properties of AlSi12CuNi alloy fabricated by Selective Laser Melting (SLM) were investigated. Wide range of laser irradiation conditions were selected to optimize the process in terms of optimum volume density. As a result, fabricated objects with a relative density of 99% or higher and no crack could be obtained. The as-fabricated alloy exhibited significantly good mechanical properties; an ultimate tensile strength, a breaking elongation, and micro-hardness in comparison with the conventional die casting AlSi12CuNi alloy. The fine microstructures composed of the α-Al phase and nano-sized eutectic Al-Si network could be observed. The dimensions of the microstructures were smaller than that of the conventional die casting AlSi12CuNi alloy. The superior mechanical properties were attributed to the microstructure associated with the rapid solidification of the SLM process. The influence of building direction of mechanical properties on fabricated objects was evaluated. The ultimate tensile strength and breaking elongation were significantly affected by the building direction, which was higher in the case of a parallel direction to the roller moving direction. AlSi12CuNi alloy with good characteristics can be successfully fabricated by the SLM process.