This study investigates the relationship of second language (L2) writing skills proficiency with the first language (L1) writing skills, in light of the language transfer. The study aims to analyze the positive effects of L2 writing proficiency on L1 writing proficiency. Forty native Turkish-speaking university students participated in the study. While 20 of them attended a two-semester-L2 writing course, the other 20 students did not take any writing courses in L2. At the end of the course, all of the students took an essay writing exam in L1. They were asked to write an essay on education. The exam scores prove that writing skill transfer from L2 to L1 is possible in adult English as a Second Language (ESL) learners. The study illustrates that L2 learning and acquisition enable L2 writing skills transfer from L2 to L1; and this can bring about a progress in their first language writing skills.