The study aims to investigate the effect of using constructivist learning model in teaching science, especially in the subject of light: its nature, mirrors, lens, and properties, on the achievement of eighth-grade students and their scientific thinking. The study sample consisted of (136) male and female 8th graders were chosen from two basic schools in Tafila in the scholastic year 2015/2016. The four-class sample was divided into two groups (controlled & experimental). For achieving the study aims, the researcher prepared lesson plans using constructivist learning model, achievement test and scientific thinking test, which validity and reliability were checked. To answer the questions of the study, means, SD, ANOVA and ANCOVA were used to determine the differences in means of the groups of the study. The results show that there is statistically significant difference at (a = 0.05) for the effect of the constructivist Learning model on the achievement and scientific thinking in favor of experimental group, and there is no statistically significant difference at (a = 0.05) for the constructivist Learning model on the achievement and scientific thinking attributed to gender, and there is no statistically significant difference at (a = 0.05) for the dual interaction between teaching method and gender on the achievement and scientific thinking. In the light of the study results, the researcher presented a number of recommendations including: extra attention should be given to employ constructivist learning model within science courses, and conducting further studies about the effect of the constructivist Learning model on various learning outcomes.