OBJECTIVE: To evaluate long-term success of cranial cervical decompression for management of canine Chiari-like malformation with syringomyelia (CM/SM). STUDY DESIGN: Retrospective clinical study. ANIMALS: Cavalier King Charles spaniels (n=15). METHODS: After diagnosis by magnetic resonance imaging (MRI) dogs had cranial cervical decompression with durotomy. Seven dogs had the durotomy patched with biocompatible collagen matrix. Clinical outcome was monitored for >12 months. RESULTS: All dogs either improved (80%) or were unchanged (20%) postoperatively. Postoperative MRI in 6 dogs revealed persistence of syringomyelia. Seven dogs (47%) subsequently deteriorated, 0.2-2.3 years after surgery (mean, 1.3 years) and 2 dogs were eventually euthanatized as a consequence. Twelve dogs were still alive, 1-6.5 years after surgery (mean, 2.5 years). CONCLUSION: Cranial cervical decompression surgery is associated with low mortality and morbidity, and results in clinical improvement in most dogs. The procedure seemingly does not result in syrinx collapse and resolution. Clinical improvement may not be sustained and some dogs can be expected to deteriorate. Clinical RELEVANCE: Cranial cervical decompression surgery may have a role in management of CM/SM. In dogs with severe pain, it can improve quality of life for several years; however, it does not appear to adequately address the primary cause of syringomyelia. Further prospective study is needed to better understand the pathogenesis and treatment of this disorder. Because this condition causes neuropathic pain but does not necessarily result in euthanasia more information is needed on appropriate pain management for these patients.