Posterior Tibial Tendon Insufficiency (PTTI) is the major reason for acquired flat-foot. The purpose of this study, which was planned as a single-group pre- and post-intervention repeated measures design, was to investigate whether orthotic intervention is effective in treating pain caused by PPTI. Ten males and 15 females, whose mean age was 30.66 ± 12.67 years, completed the pain and disability subscales of the foot function index at their first visit and after 6 weeks of orthotic wear. There was a 47.64% decrease in pain and a 53.07% decrease in disability levels, and a high correlation between pain and disability subscales. The results of our study imply that orthotic management of PTTI is effective in alleviating pain and the amount of difficulty expressed by the patient.