The purpose of this study was to determine the relationship between organizational citizenship behavior (OCB) and personality in experts of Sport Organization of Tehran Municipality. The research was descriptive and correlational. Statistical sample equaled the statistical population (N=90), but only 83% of their data were analyzed. Demographic questionnaire, organizational citizenship behavior questionnaire (?=0.75) and personality (Big five model) questionnaire (?=0.71) were used in this study. Descriptive and inferential statistics (Pearson correlation, Spearman and Kolmogorov-Smirnov test) and SPSS13 and EXCEL software were used to analyze the data. The results showed that statistical sample (N=75) consisted of 57.3% men and 42.7% women. Most experts were young (54.7%) and aged between 25 and 30. They had an occupational career between 1 and 3 years (68%). There was a significant positive relationship between OCB and personality. There were also positive significant relationships between OCB and conscientiousness and OCB and eagerness for experience (P<0.05). There was no significant relationship between OCB and mediator variables (age, gender and occupational career) (P>0.05).