The purpose of this study is to evaluate the English language proficiency of Sayed Jamaluddin Afghani University students enrolled in the English Department. It primarily looks at the grammatical mistakes that impede kids' language development and how they affect their ability to communicate. A structured questionnaire was used in a quantitative survey with a sample of 120 students in order to collect data. The results show that improper application of linguistic norms, infrequent practice, and the effect of students' native language, which frequently interferes with English usage, are the primary causes of grammatical errors. The efficacy and clarity of students' speech are greatly impacted by these errors. According to the study's findings, English professors should implement specialized courses that emphasize communicative grammar instruction. It also recommends giving students regular chances to practice active language usage, which can improve their overall communication skills and grammatical precision, ultimately increasing their English proficiency.