Objective: To investigate whether orthotic treatment is effective for the treatment of posterior tibial tendon dysfunction stages I and II (flat foot). Data Sources: Five databases (PubMed, Scopus, PEDro, SPORTDiscus and The Cochrane Library) were searched for potential RCTs from their inception until August 2020. Review Methods: Only randomised controlled trials (RCT) that included subjects diagnosed with posterior tibial dysfunction in the initial stage and treated with orthotic treatments were selected. The outcomes assessed were whatever symptom related to posterior tibial tendon dysfunction stage I and II. Included RCTs were appraised using the Cochrane collaboration risk of bias tool. Results: Four RCT articles and 186 subjects were included. 75% were at high risk of bias for blinding of participants and personnel. Three different types of conservative treatment were used in the studies: foot/ankle-foot orthoses, footwear and stretching /strengthening exercises. Foot orthoses, together with exercise programmes, seemed to improve the effect of orthotic treatment. Foot orthoses with personalised internal longitudinal arch support were more effective than flat insoles or standard treatments in reducing pain. Conclusions: The use of orthotic treatment may be effective in reducing pain in the early stages of posterior tibial tendon dysfunction. Further research is needed into individualised orthotic treatment and high-intensity monitored exercise programmes.