The aim of the present study was to find out the Effect of Constructivist Approach on Achievement in Science at Elementary Level. Experimental research design was employed in the study. A sample of 60 students were selected and grouped intoexperimental group (30) and control group (30). The experimental group was taught through constructive approach and control group was taught same topics with traditional method of teaching. For these 20 lesson plans has been developed by Investigator from selected topics of science, in which 10 lesson plans based on constructivist approach (7E model) and other 10 lesson plans based on traditional method.The study found that there is found significant difference in the effect of constructivist approach on achievement in science of students of control group and experimental group. The study concluded that constructivist approach is largely helpful in enhancing the achievement level in the subject of science.