This research aimed at improving some EFL grammatical competence among first year preparatory school pupils through using interpersonal and intrapersonal intelligences. The participants of the study consisted of 30 first year preparatory school pupils in Alshahid Mahmoud Abdelazim Mahmoud preparatory School, in Kafr Farsis, Benha, Qaliupia Government. The research followed the two-groups (experimental and control groups) pre-post test design. The Pre grammatical competence test was administered to the two groups of first year preparatory school pupils. The pupils were taught using interpersonal and intrapersonal intelligences to develop their grammatical competence skills. Then, the post-test was administered again. T-test was used to compare the mean scores of the experimental group and control group of the pre-post test. Results of the analysis revealed that the participants' EFL grammatical competence skills of the experimental group improved significantly than the control group as a result of using interpersonal and intrapersonal intelligences. Therefore, it can be concluded that the interpersonal and intrapersonal intelligences was effective in developing EFL first year preparatory school pupils' grammatical competence skills.