This study aimed at investigating the effect of teaching by computerized math's games on the third grade students' achievement in multiplication and division , retention achievement and their attitudes towards mathematics . The sample of the study consisted of ( 48 ) students who were divided into two equivalent groups : the experimental group consisted of ( 24 ) students were taught by using the computerized math's games. Whereas, the control group was taught by the normal method and it consisted of ( 24 ) students . An achievement test and attitudes towards mathematics scale were used after calculating their reliability and validity. The reliability coefficient of the achievement test was (0.75 ) and the reliability coefficient of the attitudes towards mathematics scale was (0.84). ? T-test of the independent sample was used and the result showed that there was statically significant difference at (a <0.05 ) between the means of the third graders scores in the achievement , retention achievement and attitudes towards mathematics of the experimental and the control groups in favor of the experimental group. The researcher recommended producing computerized math's games programs with a guide to use them in teaching by the Ministry of Education in the Sultanate of Oman supplemented with school books and to implement workshops for teachers on how to use them in teaching The researcher suggested conducting further studies in the field of computerized math's games and their relationship to students' levels of achievement and types of thinking.