Abstract： Objective:To retrospectively evaluate the clinical efficacies and radiological outcomes of calcaneo-cuboid-cuneiform osteotomy for flexible flatfeet in children.Methods:From August 2015 to August 2019, a total of 12 children (18 feet) with flexible flatfoot underwent calcaneo-cuboid-cuneiform osteotomy (3C osteotomy). Operative age, operative duration, intraoperative volume of blood loss, duration until removal of internal fixation and the latest follow-up imaging data were recorded. Clinical outcomes were evaluated by Visual Analog Scale (VAS) pain score and modified American Orthopedic Foot & Ankle Society Scale (AOFAS). A total of 6 parameters on anteroposterior (AP) and lateral radiographs of foot in weight loading were compared, including AP talo-first metatarsal angle, lateral talo-first metatarsal angle, AP talocalcaneal angle, lateral talocalcaneal angle, talo-navicular coverage angle and calcaneal pitch angle.Results:Mean operative age was (11.7±3.6) year, mean operative duration (93.1±15.8) min, mean volume of intraoperative blood loss (41.9±19.9) ml and mean duration until removal of internal fixation (13.2±7.0) months. All of them were followed up for at least 22 months with an average of 31 months. Preoperative VAS pain score dropped sharply from (5.08±0.36) to (0.92±0.19) at the final follow-up ( P<0.05). Preoperative AOFAS score improved significantly from (42.9±6.7) to (82.9±6.3) at the final follow-up ( P<0.05). Postoperatively, 5/6 radiographic parameters showed significant improvements as compared with preoperative values ( P<0.01). There was no postoperative instance of nonunion, osteomyelitis or wound infection. And 11/12 cases achieved satisfactory outcomes. Conclusion:3C osteotomy may achieve satisfactory outcomes for flexible flat feet in children without serious complications.