Closure of cranial sutures progresses with age; therefore, macroscopic assessment of cranial sutures has been used as one method of age estimation. Postmortem computed tomography (PMCT), which many forensic medical departments and institutes have begun to adopt, has the potential to simplify the gathering of information from cranial sutures for both surface and cross-sectional evaluation. To examine the feasibility of age estimation by cross-sectional multidetector computed tomography images of the sagittal suture, PMCT findings of 125 subjects of known age and sex were retrospectively reviewed. The sagittal suture was divided into four segments, and 20 cross-sectional slices from each segment were analyzed. These slices were each categorized by visual evaluation into one of the seven stages defined by Harth et al. according to the degree of closure. The mean stage value of 20 slices was calculated for each segment. We were able to evaluate cross-sectional images of the sagittal suture by PMCT, and a positive correlation between age and closure degree was observed. Despite the prediction interval achieved with this method not being superior to traditional macroscopic or flat-panel CT assessment, multidetector CT is a potentially useful tool, in conjunction with other methods, for age estimation, particularly in adult females and in cases where only a skull is the sole remain.