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In this investigation, the hypereutectic in-situ Al-X wt. %Mg2Si (X=15, 20, 25 and 30) composites have been developed through gravity casting technique with the use of commercially pure Al, Si and Mg metals. This composite comprises of three phases, namely the primary Mg2Si phase, which is formed during the pseudo-eutectic transformation at the time of solidification engulfed by the matrix (α-Al) and the binary eutectic (Al-Mg2Si) phase. Microstructure evaluation and the mechanical properties of these composites has been investigated. It is observed that the change Mg2Si concentration has a great impression not only on the morphology and volume fraction but also in the hardness of all the phases that exist. The size and volume percentage of Mg2Si particle increases with the increase in Mg2Si concentration. Bulk hardness also increases with higher Mg2Si concentration. The micro hardness of the reinforcement (primary Mg2Si) particle decreased slightly with the increase in the Mg2Si concentration due to the less compact particle. On the contrary, the micro hardness of the other phases showed a gradual rise with the rise in Mg2Si concentration. The higher values of Quality Index, % elongation, ultimate tensile strength and toughness are achieved in the samples where the Mg2Si concentration is nearer to the pseudo-eutectic (13.9 wt. %) region. The yield strength, firstly shows a rising trend up to 25 wt. % Mg2Si and then decreases at 30 wt. % Mg2Si concentration.