The purpose of this study was to explore white matter microstructural alterations in the patients with generalized anxiety disorder (GAD) using diffusion tensor imaging (DTI) technique, and to assess neural associations with the symptom severity. Twenty-eight first-episode, treatment-naive GAD patients without co-morbidities and 28 matched healthy controls underwent DTI acquisition and clinical symptom assessments. Tract-based spatial statistics (TBSS) was used to analyze white matter microstructural abnormalities in patients with GAD, as well as their associations with clinical symptom scores in a voxel-wise manner. Compared to controls, patients showed decreased fractional anisotropy (FA) values in 7 clusters of white matter in bilateral uncinate fasciculus, body of corpus callosum, left middle cingulum (cingulate gyrus), bilateral anterior thalamic radiation and corona radiate, right anterior limb of internal capsule, bilateral inferior frontal-occipital fasciculus, bilateral superior and inferior longitudinal fasciculus, and increased mean diffusivity and radial diffusivity in widespread white matter regions. Reduced FA values in right uncinate fasciculus, left cingulum bundle showed significantly negative correlations with clinical symptom severity for Hamilton anxiety Rating Scale scores. Our findings suggest microstructural abnormalities in uncinate fasciculus and cingulum bundle play key roles in the underlying neural basis of GAD.