The Personality traitsand satisfaction are emphasized in the retention of the volunteer in non-profit organizations. The purpose of present study was to predict satisfaction by the big five personality traits of student sport Olympiad volunteers in IRAN. population consisted of all volunteers participating in male and female sport student Olympiad in summer 2010 and 131 volunteers were selected as sample by convenience sampling. Results showed thatsubscales agreebleness and consciousness predicted satisfaction significantly It is suggested that altruistic motivations and philanthropic feeling (related to conscientiousness and agreeableness ) are key characteristics of the volunteering.