Background: Existing methods of foot type classification based on foot morphology could be put into one of the 4 categories, including visual non-quantitative inspection, anthropometric values, footprint parameters and radiographic evaluation. Objective: The aim of the present study was to evaluate the clinical and functional outcome after calcaneal lateral column lengthening osteotomy in patients with symptomatic flexible flatfoot. Patient and Methods: This is clinical trial (pre-post intervention) included 18 patient with symptomatic flexible flatfoot who were admitted to Zagazig Orthopedic Department, with mean follow up period of 13.6±2.7 months. Results: Age was 9.05±1.89 with minimum 6 and maximum 13 years, and as regard sex distribution male were majority with 66.7%. There was significant improvement regarding talocalcaneal angle at anterior view from pre to 3, 6 and 12 months as it decreased from 46.94±5.19 to 29.66±2.86 at 3 months to 26.55±3.45 at 6 months and to 24.55±3.97 at 12 months. There was significant improvement regarding talocalcaneal angle at lateral view from pre to 3 months and also to 6 and 12 months. Conclusion: The advantages of calcaneal lengthening osteotomy are as follows: it is technically easy to be applied, has a low risk of neurovascular injury and low loss of blood. In addition, it allows other procedures to be applied in the future contrary to arthrodesis. If arthrodesis is required later in these feet, it will be far easier to do because of the corrected alignment of the foot.