Subarachnoid diverticulum is one of the most common causes of mid-back spinal cord issues in the Pug breed. Wellington, a 12-year-old male Pug, came to us with a 2-month history of wobbliness in his rear limbs. We performed an MRI of his spine, which showed a pocket of fluid (not a cyst) compressing the spinal cord. Surgery was chosen as the best treatment option for Wellington, and we got to work stabilizing his spine and reducing compression on the spinal cord. Wellington made a full recovery and was still normal at his seven-month follow-up.