Purpose <p>To quantitatively evaluate the compressed nerve in patients with cervical spondylotic radiculopathy (CSR) by MR diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT).</p> Materials and methods <p>DTI and DTT were performed in 60 patients and 20 volunteers with a 3.0-T MR. The resultant fractional anisotropy (FA) values and apparent diffusion coefficient (ADC) values for C5–C7 cervical nerve roots were calculated at three sub-regions and DTT was also performed on C5–C7 nerve roots. Assessment of sensory and motor function in patients was undertaken using modified Japanese Orthopaedic Association (mJOA) scoring system.</p> Results <p>The FA values were significantly lower at the symptomatic side than those at the asymptomatic side (<i>p</i> &lt; 0.05). The mJOA score was correlated with the FA values significantly of the compressed nerves at proximal sub-region (<i>R</i>^<i>2</i> = 0.393,<i> p</i> &lt; 0.001). ROC curve analysis revealed that FA values could identify nerve root compression at three sub-regions. DTT could visually display the abnormalities of compressed nerve roots, including the decreased of FA values, twisted, sparse, or interrupted nerve roots in patients with CSR.</p> Conclusion <p>MR DTI and DTT provided effective means for quantitatively evaluating the compressed nerve in patients with CSR.</p>