Flexible flatfoot is a common deformity in pediatric and adult populations. In this study, we aimed to evaluate the functional and radiographic results of subtalar arthroereisis in adult patients with symptomatic flexible flatfoot. We included 26 feet in 16 patients who underwent subtalar arthroereisis for symptomatic flexible flatfoot. Radiographic examination included calcaneal inclination angle, lateral talocalcaneal angle, Meary’s angle, anteroposterior talonavicular angle, and Kite’s angle. The clinical assessment was based on the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot scale and a visual analog scale (VAS). The mean follow-up was 15.1±4.7 months. The mean preoperative AOFAS score was 53±6.6, while the mean AOFAS score at the last follow-up visit was 75±11.2 ( P<0.05). The mean visual analog scale score was 6.9±0.6 preoperatively and 4.1±1.4 at the last follow-up visit ( P<0.05). The mean preoperative and postoperative values measured were 13.4°±3.3° and 14.6°±2.7° for calcaneal inclination angles ( P<0.05); 35.7°±6.9° and 33.2°±5.3° for lateral talocalcaneal angles ( P>0.05); 8°±5.3° and 3.3±3 for Meary’s angles ( P<0.05); 5.6°±3.5° and 2.6°±1.5° for anteroposterior talonavicular angles ( P<0.05); and 23.7°±6.1° and 17.7°±5° for Kite’s angles, respectively ( P<0.05). Implants were removed in three feet (11.5%). Subtalar arthroereisis is a minimally invasive procedure that can be used in the surgical treatment of adults with symptomatic flexible flatfoot. This procedure provided radiological and functional recovery in our series of patients.