The current study investigates the effectiveness of using Computerized Administrative Information System in Decision Making Processes in the Directorates General of Education in the Ministry of Education in the Sultanate of Oman. The population of the study consisted of (401) Persons who occupy the following jobs: Director general, Deputy Director General, Director of department, Deputy Director of department, and Heads of Section. The sample of the study was formed by (89) Persons who occupy the following job in Muscat Governorate and Al-Dakhilia region. To answer the study's questions, the researcher developed a questionnaire of 34 items divided into five sections. They were information system and decision making, convenience of the information, convenience of the programs in use, which was checked for its validity and reliability, competencies of the employees, and the effectiveness of computers The collected data was analyzed for means and standard deviations. The findings have come to insure that using computerized administrative information system in decision making processes is effective. The scored means varied between (3.88) and (3.05) as follows: 1- Information system and decision making scored the highest means amongst other sections of the questionnaire. The means varied between 4.47 and 3.51, which indicates to that the used programs used are effectives. 2- The available information in both directorates are convenience and help in decision making scoring means between 4.17 and 3. 3- The used computer programs are suitable and efficient an help the respected staff to store, recall the needed information easily. Results of the second section of the questionnaire The scored means varied between 3.48 and 3.030. 4- The competencies of employees in using the computerized information system in decision making processes was medium, scoring means between 3.47 and 2.79. Finally, the study concluded the following recommendations 1- Make sure that the used programs should suit job requirements and the process of using the programs should be easy to recall the required information and classify it. 2- Organize and run special courses for the employees working in computerized administrative information system. 3- Make sure that the qualifications of the employees who work in the computerized administrative information system match their asserted duties. 4- Increasing the effectiveness of the used computers to meet the jobs' requirements. These computers should be usually upgraded in regards to their storage capacities, and speed further to securing enough number of computers for the users.