A mother tongue plays a fundamental role in the use of other languages. The research was carried out to determine the influence of the Pashto language (L1) on the acquisition of English grammar at the elementary level in District Karak. This study employed the detailed procedure of thematic analysis technique and the Pretest-Post-test Equivalent-Groups Design for experimental design. The participants were grouped using convenient and random sampling techniques. It was found that a significant difference was observed between the scores of post-tests of the control group as well as the experimental group when the result of both groups was compared. Learners of the investigational group surpassed the learners of the control group in the domain of this particular component of grammar. It is recommended that the government should induct English teachers of the mother tongue of the learners so that they may utilize the mother tongue of the learners while teaching English grammar to their students.