Background: Surgical resection is an important treatment for early rectal cancer; however, postoperative anastomotic stenosis remains a challenging issue for surgeons worldwide. The endoscopic approach is usually first-choice treatment for patients with rectal cancer. Balloon dilatation, stent implantation, and endoscopic radial incision are common surgical approaches, with most patients obtaining satisfactory treatment results. However, these methods are ineffective for some patients, resulting in the need for repeated endoscopic balloon dilatation, surgical resection of anastomotic stenosis, or even permanent enterostomy. At present, there are no effective and non-recurrent interventions for these patients. For the patient described in this report, we used the technique of endoscopic balloon dilatation followed by an injection of fluorouracil (5-Fu), which successfully improved the clinical symptoms in this patient. Case Summary: Herein, we report on a case of a 67-year-old man who underwent a laparoscopic radical resection for the treatment of rectal cancer. However, the patient began having recurrent abdominal pain, bloating, and dyschezia at 1 year after the operation. His colonoscopy revealed a strictured rectal anastomosis. Endoscopic balloon dilatation was repeated more than 10 times, but anastomotic stenosis still worsened. Because the patient wanted to preserve the anus, a rectal anastomosis resection was not performed, and an endoscopic balloon dilatation combined with an injection of 5-Fu was performed instead. At day 1 after the surgery, the patient was able to defecate spontaneously, and rectal stricture was relieved. The patient was followed up for 21 months post-surgery. His symptoms of abdominal pain and distension did not recur, and there were no symptoms of defecation difficulty. Conclusion: Endoscopic balloon dilatation combined with an injection of 5-Fu is a satisfactory method for the treatment of anastomotic stenosis after rectal surgery.