Objective: This study presents the outcomes of patients with idiopathic degenerative and posttraumatic atlantoaxial osteoarthritis who were treated with upper cervical manipulation in combination with mobilization device therapy. Clinical features: A retrospective case review of 10 patients who were diagnosed with either degenerative or posttraumatic atlantoaxial arthritis based on histories, clinical symptoms, physical examination, and radiographic presentations was conducted at a multidisciplinary integrated clinic that used both chiropractic and orthopedic services. All 10 patients selected for this series were treated with a combination of upper cervical manipulation and mechanical mobilization device therapy. Outcome measures were collected at baseline and at the end of the treatment period. Assessments were measured using patients' self-report of pain using a numeric pain scale (NPS), physical examination, and radiologic changes. Average premanipulative NPS was 8.6 (range, 7-10), which was improved to a mean NPS of 2.6 (range, 0-7) at posttreatment follow-up. Mean rotation of C1-C2 at the end of treatment was improved from 28° (±3.1) to 52° (±4.5). Restoration of joint space was observed in 6 patients. Overall clinical improvement was described as "good" or "excellent" in about 80% of patients. Clinical improvements in pain and range of motion were seen in 80% and 90% of patients, respectively. Conclusion: Chiropractic management of atlantoaxial osteoarthritis yielded favorable outcomes for these 10 patients.