Stitch-bonded biaxial polymer matrix composite is a compromise between unidirectional composite and woven composite materials. In this paper, fatigue delamination behavior of stitch-bonded biaxial polymer matrix composites was investigated. The delamination growth rate in three domains of subcritical, linear, and unstable growth rate were studied. The effects of increased fracture resistance due to fiber bridging, multiple cracks, separation, and matrix cracking were considered in fatigue behavior of the composite. The fatigue onset life test was conducted to determine the threshold energy release rate. The total life delamination growth rate of stitch-bonded polymer matrix composites was characterized and presented.