Perinatal stroke causes most hemiplegic cerebral palsy. Understanding developmental motor plasticity after perinatal injury is key to developing new therapies. Diffusion tensor imaging (DTI) facilitates this by interrogating functional white matter tracts (e.g. corticospinal tract, CST) but is not well studied in perinatal stroke. Our aim was to quantify CST integrity following perinatal stroke with DTI, evaluating different methodologies and correlations to motor outcome. Twenty-six children (Alberta Perinatal Stroke Project) underwent standardized DTI. Fiber tracking across different CST sections and ROI analysis compared CST diffusion variable (FA/AD/RD/MD) ratios (lesioned/non-lesioned). Correlations with validated motor outcome measures (AHA, MA, PSOM) were sought. DTI quantified differences in all CST diffusion parameters. Decreased FA and increased RD in the lesioned CST demonstrated the most robust correlations with motor outcomes. Analysis of defined CST subtracts may offer advantages over traditional DTI techniques. CST DTI carries both clinical and research utility in perinatal stroke.