Educationists are of the opinion that the educational problems relating to quantity and quality could be tackled by the proper utilization of instructional technology. Instructional technology is a systematic way of designing, carrying out and evaluating the teaching learning process. Instructional technology makes instruction more effective, understandable and meaningful. All types of resources are used to make the learning easy. Traditional teacher-centred approach in the classroom has been shifted from teaching to learning. It is called student centred or resource-based approach, the student being the resource. Learning through hearing alone proves to be the least effective means of learning. One learns eleven percent by hearing as against eighty-three percent by seeing. As for as retention of hearing is concerned, learning through hearing again stands at the lowest ebb because after three days, we recall only ten percent of what we learn through hearing as against fifty percent of what we learn through both hearing and seeing, and ninety percent of what we acquire by applying three of our senses i.e. seeing, hearing and doing. The major objectives of the study were, (i) to find the relative effectiveness of instructional technology in teaching biology at secondary level to students of experimental group and control group and (ii) to see the difference of treatment effects between the students of low achievers and high achievers and high achievers, (iii) to see the difference of treatment effects between the students of the control and experimental groups on the variable of retention. The study is significant because findings identified the effectiveness of instructional technology and weakness of traditional approach at secondary level in teaching biology. The researcher selected the students of 10th class of the Federal government Girls Secondary School No.6 and two groups (experimental and control) were randomly secured from total available group. The equivalence of the groups was determined by equating the students of both groups on the pre-test scores. Four chapters of biology were taught during the experiment of both experimental and control groups by two different teachers almost of the same qualification and experience and were intended to measure the outcomes of learning. The post-test was administered to both groups after twelve weeks. The retention test was administered after twelve weeks of the post-test. In order to secure data, pre-test and retention rest were administered as research instrument. Data were tabulated, analyzed and interpreted in the light of objectives of the study. In order to see the significance of the results, the t-test was applied. The analysis revealed that the application of instructional technology as supplementary strategy in teaching biology was more effective because the use of instructional technology increased interest and enhanced motivation levels. Instructional technology as supplementary strategy was also found to be equally effective for low achievers and high achievers. On the basis of findings, researcher provided workable suggestions/recommendations for enhancing the effective learning of students of biology at secondary level.