This study investigated the Effects of Expository Method Enriched with Improvised and Standard Materials on academic Performance of Large Class of Basic Science Students , Kaduna Nigeria. The study intended to improved the academic performance, check and reduce the persistent failure among Basic Science students in large class using enriched expository method with instructional materials. The study involved pre-test, post-test quasi experimental and control group design. The population consisted of all (number of schools in study area ) which consist of a total of four thousand eight hundred and ninety-nine (4,899) students. A sample of 392 students was drawn from three schools and divided into two experimental groups and one control group. The experimental group I was taught using improvised instructional materials. The experimental group II was taught using standard instructional materials while control group was taught using lecture method without instructional materials. The instrument used for data collection was Basic Science Performance Test (BSPT) with reliability coefficient of 0.83. Five research questions and hypotheses were formulated and tested. The research questions were answered descriptively using mean and standard deviation while the null hypotheses were tested using t-test at p < 0.05 level of significant. Findings from the analysis of the data revealed that there was significant difference in the mean scores of experimental and control groups in favour of experimental groups. There was no significant difference in the mean scores of male and female students exposed to expository method enriched with improvised and standard materials after being taught Basic Science Concept using the expository method enriched with improvised and standard materials. Based on these findings, it was recommended that the expository method enriched with improvised or standard materials should be used by Basic Science Teachers to teach Basic Science Students in large class at the upper basic education level. Therefore, instructional materials that teachers use in teaching Basic Science have significant effects on students performance and the use of either improvised instructional materials in the absence of standard or convential materials can facilitate learning in large class of Basic Science.