An effective stress function utilizing the J₂ theory, which includes plasticity and damage, was investigated to predict the monotonic response of metal matrix composite (MMC). The damage considered was in the form of debonding between fiber and matrix and plasticity in the form of slip bands in the matrix. Yield surfaces were generated with consideration of both damage and plasticity in effect. The computational micromechanics analysis involved a unit cell model utilizing the ABAQUS code for analysis. The constitutive response predictions from the J₂ model were compared with experimental results from monotonic unidirectional loading for transverse tension, compression, longitudinal tension, and pure shear. The finite element analysis estimated apparent yield points at a variety of combinations of normal stresses. Both σ₁₁ and σ₂₂ were consistent with the results obtained from the effective stress function, providing a strong basis for the use of the J₂ theory to account for combined plasticity and damage response of MMCs. Good correlation was obtained between experiments and predictions.