PURPOSE Development of the Persian version of the Modified Modified Ashworth Scale (MMAS), and to investigate the interrater and intrarater reliability of the Persian MMAS when used to quantify elbow flexor spasticity in patients after stroke. METHODS The Persian MMAS was developed by the forward and backward translation procedure, a final review by an expert committee, and testing for acceptability and the clarity of item wording so that the scale could be used by Persian-speaking examiners. Psychometric testing included interrater and intrarater reliability. Elbow flexor spasticity was examined by two raters in 30 patients after stroke twice on two occasions using the Persian MMAS. The weighted κ was used for the statistical analysis. RESULTS The interrater and intrarater reliability was very good for the Persian MMAS (weighted κ: 0.81-0.91; 95% CI 0.68-0.98) with statistically significant agreement between raters and within raters (all p < 0.001). CONCLUSIONS The Persian version of the MMAS was successfully developed. The Persian MMAS showed very good interrater and intrarater reliability in patients with elbow flexor spasticity after stroke. The results support the use of the Persian version of the MMAS both in clinical and research settings.