Abstract The present study investigated the effectiveness of instrumental enrichment on developing primary language school pupils' reasoning skills and achievement in science in the first semester of the academic year (2021–2022). A quasi-experimental design was adopted. The researcher used a reasoning skills test and an achievement test as research instruments. The study sample consisted of 60 participants from fifth grade. The sample was selected from the distinguished Sherbien Official Language School and divided randomly into two groups: the experimental group (n = 30) and the control group (n = 30). The experiment lasted for six weeks, after which research instruments were applied. The results revealed that instrumental enrichment had a positive effect on students' reasoning skills and achievement. Results also revealed that there is a statistically significant difference at (α ≤ 0.05) level between the mean score of the experimental group and the mean score of the control group in favor of the experimental group in both reasoning skills achievement in science. Keywords: Instrumental Enrichment, Reasoning Skills