Writing in English as a Foreign Language (EFL) continues to pose significant challenges for senior high school students, primarily due to linguistic difficulties in writing skills. This study aimed to identify the linguistic challenges that affect students´ writing skills and to determine the correlation between these challenges and their performance on an English writing proficiency test. The research involved a sample of 81 third-year students from a public high school. Data was collected using a 30-item proficiency test that assessed knowledge of definite and indefinite articles, count nouns, and false friends. A structured questionnaire was also administered to examine difficulties focused on grammar, vocabulary, and L1 (first language) interference were the main linguistic challenges influencing students’ writing performance. However, the correlation analysis showed weak relationships between linguistic challenges and overall writing proficiency. This indicated that although linguistic competence impacts writing, it is not the only factor affecting students’ performance. The implication of this finding is that writing instruction should not focus solely on correcting grammar or vocabulary errors but should include broader instructional strategies that address cognitive and contextual. aspects of writing. In conclusion, overcoming EFL writing difficulties requires a comprehensive teaching approach that supports multiple dimensions of language learning, including linguistic, psychological, and environmental factors.