The study aimed to investigate the effectiveness of using the 4MAT model on acquiring geometric concepts and geometric reasoning among sixth graders. It used a semi experimental method, that was applied to a sample of (62) students distributed among two divisions of the sixth grade students, randomly selected from one of the schools affiliated to the Directorate of Education in the Governorate of Muscat. The students were divided into two groups: experimental group consisting of (31) students who studied the unit of geometry using the 4MAT model, whereas a control group consisting of (31) students who studied the same unit by a traditional teaching method. To achieve the research objectives, the researcher designed a teacher′s guidebook for geometric unit based on the 4MAT model. Two tools were applied for this study, which are a test designed by the researcher to examine the students acquisition of geometry concepts consists (20) items and geometric reasoning consists (15) items. The semantic validity and reliability of the study tools have been extracted in the appropriate ways and they were found to be acceptable for the study demands. The results of this study revealed differences at the level of significance (α = 0.05) between the student′s mean scores in the experimental group and control group in both geometry concepts acquisition test and geometric reasoning test for the experimental group. According to the results, the researcher recommended to conduct more studies on the 4MAT model with other variables and pay more attention to geometric reasoning by providing student′s with activities.