This study aimed to investigate the level of implementation of differentiated instruction by the English teachers and its impact on the performance of the learners. A total of ten (10) teachers and selected three hundred (300) students of Alubijid National Comprehensive High School were utilized as respondents of this study. The scores of both the pretest and the posttest were taken and these data were coded, tallied, and were statistically treated using the mean, standard deviation, and t-test of significant difference. The mean, standard deviation and t-test were used to determine the level of performance of control and experimental groups and to answer the research questions of this study. The findings revealed the overall level of teachers implementation of differentiated instruction is very high. Moreover, the overall learners academic performance shows an improvement in the groupings of learners both in the control and experimental group but shows significant improvement or higher increased of performance was observed on learners taught using Differentiated Instructions compare to the control group. Finally, significant difference was established using the learners pretest and posttest scores. Based on the above findings and conclusions, the following recommendations are suggested by the researcher that the Differentiated Instruction should be used in teaching the learners regardless the level in English especially in heterogeneous classes because it will help improve their academic   performance. Teachers should be given in-service trainings on Differentiated Instructions for them to gain more knowledge and a clear understanding of the approach.