BACKGROUND: Postoperative dysphagia is a known complication of anterior cervical surgery, but its incidence and possible mechanisms are seldom reported after occipitocervical fusion (OCF). Our objective was to study the relationship between craniocervical alignment and the development of dysphagia after OCF for the treatment of basilar invagination with atlantoaxial instability. METHODS: The study consisted of a retrospective series and a prospective series. Seventy-eight patients who underwent OCF (30 male, 48 female) were reviewed in the retrospective series. The presence and duration of postoperative dysphagia were recorded with an in-person questionnaire or telephone interview. Sagittal reconstructed computed tomography images before and after the procedure were collected. The O-C2 angle and C2-C7 angle were measured. The relationship of these parameters and their influence to the incidence of dysphagia were analyzed. The patients were grouped according to whether they developed postoperative dysphagia (group A) or not (group B). A prospective case series of 27 patients (group C) were reported to verify the influence of O-C2 angle on postoperative dysphagia. RESULTS: In the retrospective case series, 19 patients (24.4%) complained of postoperative dysphagia after OCF. The change in the O-C2 angle was significantly lower in group A than in group B (P < 0.001). In the prospective case series, only 1 patient (3.7%) complained of postoperative dysphagia. CONCLUSIONS: O-C2 angle plays an important role in the development of postoperative dysphagia after OCF procedure. Careful intraoperative alignment of the O-C2 angle may help to reduce the incidence and severity of postoperative dysphagia after OCF.