Abstract This study aimed at investigating the effect of using a flipperentiated instruction web-based program to develop primary stage pupils' EFL vocabulary learning, grammar performance and their engagement. The participants were two groups of primary six male pupils each. It adopted a quasi-experimental design employing two groups: experimental and control. The design included an independent variable (a flipperentiated instruction web-based program) and three dependent variables (vocabulary learning, grammar performance and engagement) which were measured by an EFL Vocabulary Learning Test, an EFL Grammar Performance Test and an Engagement Scale. Results revealed that there is a statistically significant difference between the mean score of the experimental and control group pupils on the post vocabulary test in favor of the experimental group. In addition, there is a statistically significant difference between the mean score of the experimental and control group pupils on the post grammar performance test in favor of the experimental group. Finally, there is a statistically significant difference between the mean score of the experimental and control group pupils on the engagement scale in favor of the experimental group. These results showed that the flipperentiated instruction web-based program had a positive effect not only on the pupils' vocabulary learning and grammar performance, but also on the pupils' engagement. Keywords: Flipperentiated Instruction, Web-based Program, Vocabulary Learning, Grammar Performance, Engagement, EFL.