This study aims at investigating the effectiveness of a group counseling program based on REBT in reducing irrational beliefs among Omani female teachers in Nizwa City in Sultanate of Oman . A non – random sample of about 18 female teachers who scored the highest in the inventory distributed in two equal groups , Experimental and control . To examine the research hypotheses a Mann Whitney test , standard deviation and mean were used in the analysis of data . The results show the following : 1- There are statistically significant differences in the means of both , the experimental and the control groups on the post – test in favor of the experimental group . 2-There are statistically significant differences in the means of both , the experimental and the control groups on the following up test in favor of the experimental group. This shows the effectiveness of the collective rational emotive counseling program in reducing teachers' irrational beliefs .