The study examined the influence of students’ perception of improvised instructional materials on learning outcomes in Accounting among SS1 students in Aba metropolis, Abia State. The study was guided by the objectives of determining the extent to which students’ perception, level of involvement, classroom environment, and school support influence learning outcomes when improvised instructional materials are used. The study adopted a descriptive survey design, targeting a population of 2,450 SS1 Accounting students across public and private secondary schools in Aba metropolis. A sample of 245 students was drawn using stratified random sampling, ensuring representation based on school type and gender. Data were collected through a structured questionnaire to measure students’ perception and involvement, and an Accounting Achievement Test (AAT) to assess learning outcomes. The instruments were validated by experts in Business Education and Educational Measurement and tested for reliability using Cronbach Alpha and test-retest methods, yielding coefficients above 0.70. Data analysis involved descriptive statistics (mean, frequency, and percentage) and inferential statistics (Pearson Product Moment Correlation) at a 0.05 significance level. Findings revealed that students generally perceive improvised instructional materials positively and are actively involved in their use. There was a significant positive relationship between students’ perception, level of involvement, and learning outcomes in Accounting. Additionally, classroom environment and school support were identified as critical factors enhancing the effectiveness of improvised materials. The study concluded that students’ perception and active engagement with improvised instructional materials significantly improve learning outcomes. It recommended that teachers integrate improvised resources into Accounting lessons, schools provide supportive learning environments, and policymakers encourage teacher training on the effective use of locally available instructional materials. The study contributes to knowledge by demonstrating that contextual, hands-on instructional resources can enhance academic achievement, particularly in resource-limited settings.