Magnetic resonance imaging was performed on a 15-yr-old captive female California sea lion (Zalophus californianus) with a 2-wk history of progressive paraparesis and a 9-mo history of exudative skin lesion on the left thoracic wall. Magnetic resonance images showed a well-defined muscle infiltrating lesion ventrolateral to the seventh cervical to the third thoracic vertebra on the left side, which extended through the left intervertebral foramina C7 to T3 into the vertebral canal, causing spinal cord compression and displacement as well as inflammation of the spinal cord and nerves. This lesion surprisingly caused no forelimb deficits. Differential diagnoses included abscess formation or neoplasia. Pathologic examination revealed chronic focal purulent meningitis associated with widespread paraspinal fistulous inflammation originating from a chronic dermal ulcer. Mainly Escherichia coli var. haemolytica and Clostridium perfringens were identified as the underlying agents.