The high temperature creep behaviors of 20 vol% SiC particulate and whisker reinforced 2124Al matrix composites and unreinforced 2124Al alloy, processed by powder metallurgy, were investigated at 300°C. The steady state creep rates of SiC/2124Al composites and 2124Al alloys followed the power law creep behavior with the stress exponent, n, of 9-10 and the activation energy, Q, of 300-360kJ/mol. The creep resistance of composites was much higher than that of the 2124Al, and the whisker reinforced composites showed the lowest steady state creep rate indicating the highest creep resistance. The effective stresses, which contribute to the creep deformation of matrix in composite, were calculated based on the concept of load transfer between matrix and reinforcement. The steady state creep rates of composites and alloy were found to be similar when the effective stress was identical. As the effective stress was sensitively dependent on the aspect ratio and alignment of SiC whiskers, an effective aspect ratio was proposed combining the effect of aspect ratio and alignment of whisker on the load transfer efficiency. The steady state creep rates of SiC/2124Al composites with different aspect ratio and alignment of SiC reinforcements were found to be similar under identical effective stress calculated by using the effective aspect ratio. These results indicate that the role of SiC reinforcements during high temperature creep of SiC/2124Al composite is to reduce the effective stress for creep deformation of matrix through the load transfer from matrix to reinforcement.