Transverse cracking in high temperature polymer cross-ply composite laminate was experimentally studied. In the tests, pristine as well as heat treated cross-ply laminate specimens were subjected to quasi-static tensile loading at room temperature and 150°C. Microscopy studies revealed that manufacturing induced transverse cracks were present in 90° layer of pristine cross-ply laminates. An increase in number of transverse cracks were observed after the heat treatment. Transverse crack density (number of cracks/unit length) growth upon applied thermo-mechanical transverse stress in 90° layer was analyzed using 3-parameter Weibull failure stress distribution. The Weibull location parameter, in efforts to address the influence of temperature and heat treatment of crack density growth, is modified based on empirical data. The predicted results were in good agreement with the test results.