ABSTRACT This research work investigated the influence of instructional materials (teaching aids) on students’ academic performance in senior secondary school Chemistry in Cross River State. A two group pre-test post test quasi-experimental design was adopted for the study. One research question and one hypothesis were formulated to guide the study. A total of 100 senior secondary one (SS1) Chemistry students were selected from five (5) Schools in Yakuur Local Government Area of Cross River State through simple random sampling and stratified random sampling techniques. Fifty SSI students (Experimental group) were taught with instructional materials and another forty (Control group) were taught without instructional materials. A validated Chemistry Achievement Test (CAT) was used to gather data for the study and a split-half was carried out using the Pearson product moment correlation to obtain a reliability coefficient of 0.67.Independent t-test was used to test the hypothesis at 0.05 significant level while the Pearson product moment correlation coefficient at that level was used to analyse the research questions. The study revealed that students taught with instructional materials performed significantly better than those taught without instructional materials and also that the use of instructional materials generally improved students’ understanding of concepts and led to high academic achievements . Recommendations were made on how to improve academic performance of chemistry students by encouraging the use of instructional materials in teaching-learning chemistry.