Grape vine is one of the important horticultural crops with unique standing as regards use and consumption. The fruit is utilized from immature to ripened state and as raisins. Its leaves can be used when they are soft and fresh. Therefore it is necessary to improve Iranian grapevine quality as well as quantity. The main purpose of this study was the use of Phenyl Phetalamic Acid (PPA) to increase fruit set and fruit quality. The experiment arranged in factorial design, included four cultivars (Razeghi, Askari, Sefidali and Rish baba) along with three concentrations of PPA (0,500,1000 mg/Lit) as based on a completely randomized design of three replications in Kashmar vineyards (Khorasan Razavi province) in spring 2010. PPA was sprayed at 50% flowering stage. Analysis of variance indicted that using PPA exerted significant effects on cluster (weight, length and number), and on berry (number, weight, length and diameter). The most fruit set index (berry number per cluster) was observed in Sefidali with 263.11 berries per cluster. Askari, Razghi and Rish baba with 113, 109.89 and 76.11 respectively, stood as the next ones. Askari and Razeghi showed similar and insignificant differences towards the reaction while their differences were significant from Rish baba. Results revealed interaction effects to be significant for cluster, berry and seed traits while insignificant for number of berries per cluster. Based on the results, cluster characteristics were affected by 1000mg/L of PPA significantly. It could positively affect the fruit set and increased it by 26.2% compared with control (except for Askari). The most effective treatment for berry characteristics was 500 mg/L of PPA that showed insignificant differences with the 1000mg/L of treatment. Finally PPA as an auxin synergist showed positive effects on grapevine fruit set, probably with a decrease in apical dominance of terminal buds and diverting metabolites to clusters, resulted in improvement of berries characteristics.