Background: Supracondylar fracture of the humerus is the most common elbow injury that requires reduction and immobilization in the proper position to union. There are a few reports regarding the position of the forearm immobilization on elbow cosmetic outcome. Objectives: This study aimed to compare two modes of the forearm, supination and pronation in elbow deformity incidence after closed reduction and casting of this fracture. Patients and Methods: This prospective and descriptive study was carried out on children with supracondylar fracture of the humerus treated with closed reduction and cast immobilization in one of the two modes of either supination or pronation for a period of three weeks. Twenty-nine patients were immobilized in supination and 35 in pronation. Follow-up lasted for 8 months. Re-displacement was defined as the criteria and subsequent deformities of the elbow in patients, were assessed by clinical and radiographic examination. Results: A total of 64 patients, 50 boys and 14 girls, with the mean age of 4.8 years (3.1 to 8.5 years) participated. All fractures were closed and of the extension type. Forty-five cases had Gartland type II and 19 had type III fracture. Deformity of the elbow had occurred in seven cases (10.94%). Four cases of cubitus varus (CA 5 o–16o) were observed in the supination group, of these, three patients had type III and one other had a type II fracture. In the pronation group, two cases of cubitus varus (CA 6 o-14 o) and one case of cubitus valgus (CA 17 o) were observed, with type III initial fracture in all 3 cases.Conclusions: In regard to elbow malunion deformity, no obvious difference was observed between the two methods of supination and pronation in the closed treatment of supracondylar humerus fracture. However, as cubitus varus and valgus had occurred in both groups with unstable type III fractures, to prevent this complication, operative fixation is advised rather than closed reduction and position of the forearm immobilization.