Background: The purpose of this study was to investigate the effect of staged surgery (open reduction/internal fixation and osteotomy) for cubitus valgus after non-union of lateral condylar fractures of the distal humerus in older children.Methods: From January 2010 to January 2013, 9 patients were treated with two-staged surgery (open reduction/internal fixation and osteotomy). The study included 5 males and 4 females, with a mean age of 12.7 years. The interval from fracture to the first surgery was 8.2 years on average. All patients had symptoms of injury of the ulnar nerve and instability of the elbow. The first surgery included internal reduction, internal fixation, and bone grafting, exposing the elbow through a lateral approach. The procedure included clearing the peripheric callus and proximal distal fracture end cicatrix with rongeur until cancellous bone was exposed, and fixation of the lateral condylar fragment with a hollow screw 4.0 mm in diameter and smooth Kirschner wire. The limb was immobilized in a long arm cast with the elbow at 90 degrees of flexion and the forearm in neutral rotation for 3 weeks, and active exercises were begun after removal. The second surgery, osteotomy of the supracondylar humerus, was completed after 6 months to correct cubitus valgus. Internal fixation from the osteotomy was removed 6 months later.Results: Six months after the second surgery, follow-up revealed that in all patients the lateral condylar fractures attained clinical union and cubitus valgus was corrected. Elbow function recovered well without arthrochalasis or humeral condylar avascular necrosis. All patients’ ulnar nerve injury symptoms disappeared.Conclusion: Staged surgery to treat cubitus valgus secondary to lateral condylar fracture non-union in older children serves to first provide elbow stability, then to correct cubitus valgus. Staged treatment may make up for the deficiencies of conventional treatment. However, due to our relatively short follow-up time, the long term effects are unknown.