A cervical rib is a rare condition in dogs and cats, but is widely described in humans. It is a congenital disorder involving the presence of additional ribs located mainly on one side or, less often, on both sides of the seventh cervical vertebra. Cervical ribs are mostly found accidentally during chest X-rays. Occasionally, however, the presence of a cervical rib can be symptomatic: neurological, cardiovascular, or respiratory symptoms are possible. An 8-year-old Shih-tzu female was presented with a progressive monoplegia of the left thoracic limb. Computed tomography revealed cervical ribs on both sides of the seventh cervical vertebra. The patient underwent surgery treatment and fully recovered.