This work presents the characterization of tembleque (SDtq) rats as a novel animal model for myelination abnormalities, primarily manifesting as tremors and ataxia, which notably declined by 16 weeks of age. This model originated from a spontaneous autosomal recessive mutation in an outbred Sprague Dawley colony. Histological and electron microscopy analyses revealed significant hypomyelination in the central nervous system of SDtq rats compared with wild-type controls. The thoracic spinal cords of SDtq rats exhibited reduced white matter areas, while the gray matter remained consistent. Peripheral nerves showed no change in myelin thickness, though a decrease in axonal diameter was observed. Transcript analysis indicated reduced expression of mature oligodendrocyte markers and increased activity of astrocytes and microglia in SDtq rats, suggesting compensatory mechanisms. Preliminary mapping studies showed that the causative mutation is located on proximal chromosome 19. These findings highlight the SDtq rat as a promising model for studying the underlying biology of myelin disorders and the role of glial cells in leukodystrophies.