The present study aimed to investigate the effect of using differentiated instruction on developing reading comprehension of sixth year primary school students. The sample of the study consisted of 64 students (males and females). The control group (n=32) received traditional reading instruction (non-differentiated), whereas the experimental group (n=32) received treatment (Differentiated Reading Instruction). Data were collected through English Reading Comprehension Test. Data collected were statistically analyzed quantitatively. For data analysis, descriptive statistics, independent samples, and t-test were used. For measuring the effect size of using differentiated instruction (independent variable) on English reading comprehension (dependent variable) of the experimental group participants, Eta Squared was computed using "t" value for the differences between the means. The study findings revealed that differentiated instruction had a great effect on developing experimental group students` reading comprehension skill as compared with the non-differentiated group. In light of these results, the study concluded that differentiated instruction approach can be used effectively for teaching reading of sixth year primary students. Finally, the study recommended that differentiated instruction should be implemented in EFL contexts.