This study investigated the effect of using activities based on the Montessori approach in science academic achievement of the fourth grade students. A quasi-experimental design was used wherein the students were equally divided into two groups: the experimental and the control group. Both groups consisted of 31 students. To achieve the aim of the study, Montessori Hall has been set up with six dimensions, and each corner has several shelves comprised different materials used for conducting the science activities. In addition, a teacher guide was prepared to be used by the teacher to implement the Montessori approach for the experimental group. Finally, an achievement test that consisted of seven multiple choice questions (MCQs) and five short answer questions was constructed and administered to both study groups. The results of the study indicated that there were statistically significant differences at the level of significance (P = 0.05) between the mean values of the experimental and the control groups in the academic achievement in favor of the experimental group. In light of the study results, the study recommends holding training workshops for teachers on how to use the Montessori approach in teaching science classes.