The age hardening behavior of SiCw/Al-2.3mass%Li-2.8mass%Cu alloy composites fabricated by the squeeze casting method was investigated using micro Vickers hardness, calorimetric technique and TEM observation. The composites showed remarkable age hardening, and the age hardening of the composites was more accelerated with increasing SiC whisker volume fraction. The composites aged at 423K showed a hardness increase of two stages, while the unreinforced matrix alloy showed a monotonous hardness increase. It was clarified that the first stage of hardness increase of the composite was due to the precipitatign of δ' (Al3Li) phase and the second one was mainly due to the precipitation of T1 (Al2CuLi) phase. In composites, the T1 phase precipitates became dominant with increasing SiC whisker volume fraction and controlled the age-hardening rate at 423K, because the T1 (Al2CuLi) phase precipitated preferentially on dislocations generated during quenching after the solution treatment due to the difference in the thermal expansion coefficient between the SiC whisker and matrix.