In an attempt to provide an empirical approach on why teaching aids remain invaluable in teaching and learning encounter, this work investigated on the effectiveness of instructional materials in teaching and learning of economics in public secondary schools in Onitsha. Four research questions and one hypothesis were formulated. 100 respondents composed of 10 permanent economics teachers and 90 students of SS2 (Science classes) were selected through simple random sampling technique. Questionnaire and teacher-made test achievement were used to collect relevant data. Simple percentage was used to analyze the research questions while T-test was used to test the null hypothesis. The study revealed that there is a positive significant difference between the mean performance of students taught with instructional materials and the mean performance of students taught without instructional materials. It was recommended that all players in the educational system should make ceaseless efforts towards encouraging and sustaining the procurement, production, storage and utilization of educational media in teaching and learning of economics in our secondary schools.