The main purpose of this study was to investigate the effects of improvised Instructional materials (IIMs) and 5E constructivist approach the teaching of acids and bases concept of chemistry. Quasi experimental research design was employed. Two grade (primary) classes were selected experimental (N=28) and control (N=34) groups. The students in the experimental group were instructed with the IIMs and 5E instructional model of constructivist approach, and students in control groups were instructed with Traditional teaching instructional for two weeks. Acids and bases were concepts tested. Classroom observation and informal classroom assessment were used as data collection instruments. Pre-test and post-test were analyzed quantitatively (comparative, descriptive statistics and independent sample t-test) while classroom observation and informal classroom assessment were analyzed qualitatively. There was a statistical significant mean difference between control and experimental group students at p<0.05. The post-test comparison of the students in experimental group demonstrated changes in conceptual understanding of the acids and bases concepts compared to the control group. Similarly, the post informal classroom assessment comparison of students in experimental group showed a higher explaining and reasoning ability of the concepts compared to the control group. Based on the finding, the researcher suggested that science teacher should use IIMs and 5E learning cycle model of constructivist approach in chemistry learning/teaching process. From the results, it is possible to conclude that the IIMs and 5E instructional model of constructivist approach were more effective than traditional teaching instructional in students’ conceptual understanding