The aim of this study was to investigate the effects of the dual task training and balance training on balance indices in subjects with functional ankle instability. This randomized clinical trial was performed in Zahedan University of medical sciences, in 2015 2016. 32 Subjects with functional ankle instability were selected through non probability sampling method. The subjects were selected based on following inclusion criteria: Functional ankle instability with at least one ankle sprain in the last year and feeling the giving way, The absence of mechanical instability of ankle by performing the anterior drawer test and talar tilt test, history of dizziness and fainting, Pain or swelling in the ankle, Impaired vision or hearing or speech, hip and lower extremity musculoskeletal disorders, feeling any pain and discomfort in the body and age between 18 to 52 years. Exclusion criteria included: The reluctance of patients to continue treatment, worsening of symptoms during the study, another treatment during investigation, given the patient's lack of progress in the early stages of attention training. The subjects were randomly allocated to two groups: dual task training group and biodex balance training group. Each of the two the two groups received their interventions for 4 weeks and 3 sessions per week. Before and after the period of the interventions, overall, anteroposterior and mediolateral stability indices were measured through the postural stability test of biodex balance system.