This study aimed to discover the effect of the Edelson's model on the acquisition of the circle geometry concepts of the students in the ninth grade and their motivation towards geometry. To achieve the objective of the study, the teacher's manual was prepared in the circle geometry unit according to the Edelson's model. The researcher also prepared two tools for this study: a test to measure the acquisition of geometric concepts, and a scale of student motivation towards geometry, and their sincerity and stability were measured on a survey sample. The study sample consisted of (58) students from the ninth grade students on basic education in one of the schools in Muscat Governorate. They were divided into two groups: an experimental group consisting of (29) students who studied the circle geometry unit using the Edelson's model and controller group who studied the same unit by atraditional method. For the analysis of the data, the study used arithmetic means, standard deviations and ANCOVA. The study found that there was a statistically significant difference at the mean level (a = 0,05) between the mean scores of the ninth grade students of the experimental and control groups in the post-test for Acquisition of geometric concepts, and motivation scale toward geometry, in favor of the experimental group. In the light of the results, the study recommended that teachers should be encouraged and trained to use the Edelson's model in the teaching of mathematics because it has a positive effect on the acquisition of concepts and raising the motivation of students towards geometry. The study also recommended the importance of conducting research studies to investigate the effect of the model in other dependent variables.