The current study seeks to highlight the use of the Van de Walle model of mathematical representations in teaching, and aimed to investigate the effectiveness of teaching the equations and inequalities unit according to the Van de Walle model of mathematical representations in algebraic understanding and self-efficacy among eighth grade female students. The study adopted the semi-experimental approach. The sample of the study consisted of 68 female eighth-grade students in a basic education school in South Al Batinah Governorate in the Sultanate of Oman, and it was divided into two groups, an experimental group consisted of 34 female students, and a control group consisted of 34 female students. Where the experimental group was taught the prescribed unit using the Van de Walle model for mathematical representations, the control group was taught the same unit in the usual teaching method. To achieve the objectives of the study, the researcher prepared a teaching guide to teach the unit of equations and inequalities according to the Van de Walle model for mathematical representations. The researcher also prepared a test for algebraic understanding consisting of 9 questions and developed a scale for measuring self-efficacy in mathematics consisting of 18 statements, using the theoretical literature and previous studies. The validity and reliability of the tools were verified, and they were found suitable for the purposes of this study. The results showed that there was a statistically significant difference at the significance level α = .05 between the mean scores of the students of the experimental group (studied according to the Van de Walle model) and the control group (studied in the usual way) in algebraic comprehension as a whole and in each of its components in favor of the experimental group. As well as the presence of a statistically significant difference at the significance level α = .05 between the mean scores of the students of the experimental group and the control group in self-efficacy in mathematics as a whole and in each of its axes in favor of the experimental group. In light of these results, the study recommended the importance of using the Van de Walle model for mathematical representations in teaching, training teachers to apply it, and conducting similar research studies to investigate the effectiveness of the Van de Walle model on other variables and other educational stages.