Aluminum Matrix Composites (AMCs) are important group of advanced engineering materials. The properties of the composites are influenced by the chemical nature of the components, morphology of particles, their spatial distribution and interface interaction. The high volume fraction of a fine and thermally stable reinforcement yields good mechanical properties of the composite. These materials have developed in many industrial fields such as aerodynamic and military application, because of their particular properties. Composites usually are fabricated from matrix phase and reinforcement phase. Among the industrial metals, aluminum and its alloys dedicated the most applications as the matrix in composites to itself; it has high strength to weight ratio and suitable ductility. In this study, it was fabricated the aluminum matrix composite with hybrid reinforcement particles of Al 2 O 3 /Al 3 Ni by in situ process in liquid state. The in situ fabrication technology for processing the MMCs involves a chemical reaction resulting in the formation of fine, uniformly distributed and relatively stable reinforcements with clean interfaces. NiO powder and ball milled NiO powder with different particle size through several stages was injected into the aluminum melt by inert gas Argon to be occurred the aluminothermic reaction and to be achieved the in situ hybrid reinforcements in the matrix (Al+XAl+MO?XAl+Al 2 O 3 +M). In order to increase possibility of in situ reaction, the melt was stirred by a mechanical stirrer. During the experiment, it was emitted a bright yellow from the furnace. This can be an evidence to occur of the in situ aluminothermic reaction. The synthesis temperature of the reaction between aluminum and nickel oxide was predicted on the basis of Al-Ni binary phase diagram and the activation energy of this reaction was determined using thermodynamical data and equations. The DTA result shows that the initiation temperature of reaction is 670°C. The composite slurry founded into the metallic mould after injecting NiO powder to the melt. Occurring in situ reaction between NiO particles and melt of aluminum leads to NiO reduction by aluminum. Also released Ni reacts with melt of aluminum that is led to fabrication of metallic compound Al 3 Ni. This compound also acts as reinforcement in the aluminum matrix. In order to characterization of fabricated composite samples, the optical microscopy, Scanning Electron Microscopy (SEM), and Spectroscopy Dispersive Analysis (EDS) was used. EDS results show that alumina particles have been distributed in the matrix. Also, the formation of Al 3 Ni phase is identified by microscopic observation. Performing the experiment in higher temperatures show that the wetability of NiO particles is enhanced with increasing the temperature. Also some mechanical tests such as tensile test, hardness test, and micro hardness were carried out in order to characterize of hybrid particle reinforcements effects. The study of properties of fabricated composite samples shows that the tensile strength and hardness of these samples increases and their elongation decreases. Keywords AMCs, aluminothermic reaction, in situ process, hybrid reinforcement particles, wetability, alumina.