Objectives: This study aimed to investigate spontaneous tongue muscle reinnervation after long nerve resection for severe hypoglossal (XII) nerve injury in adult rats. Methods: The right XII nerve was exposed, and a 9-mm section was resected. The tongue was removed and cut coronally at 4, 8, and 12 weeks after the XII nerve resection. The sections were processed for immunohistochemical staining for vesicular acetylcholine transporter (VAChT) to detect the regenerated right XII and the uninjured left XII nerve terminals. The numbers of VAChT-positive nerve terminals were counted on the injured right and uninjured left sides, and the reinnervation rate, which is the percentages of the number of VAChT-positive nerve terminals on the injured side relative to that on the uninjured side, was calculated. Results: The injured XII nerve gradually regenerated in the tongue after the nerve resection. The reinnervation rates in nerve-resected rats were significantly lower than those in normal rats, with mean reinnervation rates of 13.9%, 37.9%, and 41.8% at 4, 8, and 12 weeks after nerve resection, respectively. Conclusion: Spontaneous reinnervation occurred in the tongue muscle after the XII nerve injury with long nerve resection and injured nerve terminals regenerated approximately 40% of the normal value; this rate was considerably lower than that with the nerve transection.