Many studies suggest diabetes influences ankle fracture surgical outcomes, but results after immediate surgical treatment of closed ankle fractures (CAFs) in patients with preoperatively neglected type 2 diabetes (PND2) have not been documented. We contrasted the results of the immediate operation on CAF in 36 PND2 patients with those of a matched group of non-diabetic patients, using a case-controlled study. Outcomes were complications and ankle scores during the first 12 months of treatment. Compared with non-diabetic patients, immediate surgical fixation of the CAF in PND2 patients showed similar ankle scores. Immediate surgery in PND2 patient with CAF may increase the risk of postoperative infection compared to non-diabetic controls, but the difference was not statistically significant and did not worsen the final prognosis. These findings suggest that immediate surgical intervention is appropriate in CAF patients with type 2 diabetes.