A 5‐year‐old, domestic, shorthair, male, neutered cat was referred to the Companion Animal Clinic with a history of paraparesis and urinary incontinence, alongside recurrent urinary tract infections. Magnetic resonance imaging of the lumbar vertebral column revealed a space‐occupying spinal cyst‐like lesion located at the level of fifth and sixth lumbar vertebrae. Surgical treatment consisted of dorsal laminectomy and durectomy, resulting in decompression. Histopathology findings were indicative of spinal arachnoid diverticulum. Postoperatively, the cat exhibited gradual hindlimb and tail motor improvement, and recovery of voluntary urination. Complete resolution of the neurological signs was achieved at 3 months after surgery. No signs of recurrence were noted till the time of writing this report, 14 months postoperatively. To the authors’ knowledge, this is the first case report of a spinal arachnoid diverticulum in the lumbosacral vertebral column in a cat.