Study Design. Analysis of a combined prospective dataset. Objective. To compare clinical outcomes in patients with and without preexisting depression or bipolar disorder undergoing surgery for degenerative cervical myelopathy (DCM). Summary of Background Data. Psychiatric comorbidities, including depression, have been associated with worse clinical outcomes after lumbar spine surgery; however, it is unclear whether these psychiatric disorders are also predictive of outcomes in patients undergoing surgery for the treatment of DCM. Methods. Four hundred and one patients with symptomatic DCM were enrolled in the prospective AOSpine International or North America study at twelve North American sites. Patients were evaluated preoperatively and at 6, 12, and 24 months using the modified Japanese Orthopedic Association scale (mJOA), Nurick score, Neck Disability Index (NDI), and Short-Form 36v2 (SF-36v2) Health Survey. A mixed model analytic approach was used to evaluate differences in outcomes at 24 months among patients with and without psychiatric disorders, while controlling for relevant baseline characteristics and surgical factors. Results. Ninety-seven patients (24.19%) were diagnosed with preexisting depression or bipolar disorder. There were more females (65.98%) with these psychiatric disorders than males (34.02%) (P< 0.0001). Patients with psychiatric comorbidities were more likely to have cardiovascular (P = 0.0177), respiratory (P < 0.0001), gastrointestinal (P < 0.0001), rheumatologic (P = 0.0109), and neurologic (P = 0.0309) disorders. At 24 months after surgery, patients in both groups demonstrated significant improvements on the mJOA, Nurick, NDI, and SF-36v2 Physical Component Score (PCS). Patients with depression or bipolar disorder, however, did not exhibit a significant or clinically important change on the SF-36v2 Mental Component Score (MCS). There were no differences in mJOA and Nurick scores at 24 months among patients in each group. Improvement in NDI, SF-36v2 PCS, and MCS, however, were smaller in patients with depression or bipolar disorder than those without. Conclusion. Patients with depression or bipolar disorder have smaller functional and quality of life improvements after surgery compared to patients without psychiatric comorbidities.