The aim of this study is to determine the relationships of Turkish-English Language Teaching (ELT) learners' perceptions of learner autonomy with ELT learner's proficiency level in language learning. Particularly, the study aimed at investigating to what extent ELT learners' autonomy perceptions are affected by proficiency level of learners. Participants of the current study were 326 learners in 10 different classes aging from 18 to 23 with different levels varying from beginner, elementary, intermediate, high intermediate to advanced. The proficiency level of the learners is determined by specific exam named ALCPT(American Language Placement Test) which is administered to learners in each term and of which Cronbach alpha level is 0.98. The current study was implemented in a public institution offering four-year university education setting where the learners are academically educated on four major engineering departments, i.e. aeronautical, electronics, industrial, and computer. Data from the questionnaire was analyzed with the help of SPSS 22 by applying descriptive statistic and One-Way ANOVA statistic. Data indicated that there isn't a significant difference between learner autonomy perceptions of learners and their proficiency levels. However, data indicated that there are significant differences in the constructs of technical perspectives on learner autonomy, benefits of learner autonomy to language learning, the role of the teacher in promoting autonomy and proficiency and learner autonomy.