Purpose - An examination of the research literature suggests that no attempt has been made to examine learner autonomy development within female university-level English as a Foreign Language (EFL) students in the Kingdom of Saudi Arabia. Given that English has become the world’s predominant lingua franca for academia, business, and politics, the purpose of this paper, therefore, is to fill this gap in the literature. Design/methodology/approach - This is a qualitative case study that aims to explore learner autonomy in vocabulary development. Findings - The results showed that teachers are cognizant of the concept of learner autonomy. However, they are not all certain of the benefits of autonomous vocabulary learning. This study reveals how six adult learners’ levels of autonomy are highly influenced by their teachers’ practices. This study draws out suggestions for English language teachers who promote learner autonomy theory and practice. It also offers specific guidance, models, and adapted learning approaches of how to promote autonomy inside the classroom. Research limitations/implications - This study encountered several limitations. The first is time: the study took place over the course of two months in the Summer of 2016, when students were fully encumbered with schoolwork and social duties. The recruitment of participants during that time was a challenge. Some of the students who agreed to participate in the study were not fully engaged in the research. Additionally, the study faced difficulties with faculty commitment – one of the professors delayed the interview session multiple times and perceived some of the interview questions negatively. In addition, Dickinson’s (1993) characteristics of learner autonomy are largely related to the opportunities that are presented to the students by the teacher. It appears that Dickinson’s scale was meant to be used to identify students’ level of autonomy, particularly inside the classroom. However, because of some of the examples of activities pertaining to how they learned vocabulary outside the classroom, they were not related to classroom teaching. Also, the number of the participants is limited in this study. Practical implications - A future study could be undertaken to measure and quantitatively analyze learners’ vocabulary development on a larger scale. Research could also be conducted using a pretest, an intervention, and a posttest to measure the effectiveness of learning vocabulary autonomously. In addition, other pedagogical approaches could be utilized to measure EFL students’ intrinsic motivation and autonomy, which play critical roles in learning. Allowing learners to self-select their preferred method of learning can help them to develop their vocabulary knowledge. The findings from this study reveal that learner autonomy plays a significant role in enhancing EFL students’ vocabulary development. Originality/value - When students learn vocabulary autonomously, they are better able to source the lingua franca’s core pronunciation of a word and its spelling without the influence of the teacher’s cultural background. Given the magnitude of teachers’ workloads, they may lack the time for designing lessons that adequately meet the needs of diverse learners. Therefore, the practical way to ameliorate the problem of inadequate time is to provide them with methods (e.g. using strategies such as inquiry-based learning, problem-based learning, and project-based learning) that they can use to more readily foster learner autonomy.