The study aimed to investigate the effectiveness of teaching the symmetry unit according to Alan Hoffer's model on geometric thinking and attitudes towards geometry among seventh-grade female students. The study adopted the experimental approach with a quasi-experimental design. The study sample consisted of 69 seventh-grade female students in Al Dhahirah Governorate in the Sultanate of Oman. This sample was divided into two groups: an experimental group of 35 students who were taught using Alan Hoffer's model, and a control group of 34 students who were taught using the usual method. To achieve the study objectives, the researcher prepared a geometric thinking test covering its first three levels (Visualization, Analysis, and Informal Deduction), consisting of 18 items. Additionally, an attitude scale towards geometry was developed, comprising three fields (confidence in learning geometry, perception of the benefits of learning geometry, and enjoyment of learning geometry) with a total of 29 statements. The results showed statistically significant differences at the significance level (α ≤ 0.05) between the average scores of the experimental group students who were taught using Alan Hoffer's model and those of the control group students taught using the usual method. These differences were observed in the geometric thinking test as a whole, in each of its three levels, and in the attitude scale towards geometry as a whole and in each of its fields, favoring the experimental group. In light of these results, the researcher recommended that curriculum developers incorporate Alan Hoffer's model to enrich curriculum content with experiences aligned with students' levels of geometric thinking. Additionally, the study suggested training new teachers to use Alan Hoffer's model, encouraging mathematics teachers to focus on assessing and developing their students' levels of geometric thinking, and emphasizing the importance of fostering positive attitudes towards geometry. The study also recommended conducting further research to explore the effectiveness of Alan Hoffer's model in different research variables.