Students in higher education are expected to be autonomous and to become co-owners of their learning. In practice, they need support to advance their autonomy, and formal education is assigned an important role in this development. In order to optimally support the advancement of learner autonomy, educators should be able to define, identify and measure autonomy. Many models and approaches for measuring learner autonomy have been proposed, but as they were mainly developed for research purposes, they are not well suited for implementation in everyday teaching. This study aimed to design a tool to measure language learner autonomy in higher education that is easy to administer and interpret. The Self-Efficacy Questionnaire of Language Learning Strategies (SEQueLLS) blends the constructs of self-efficacy and learner autonomy. This article clarifies the intersection of both concepts, before outlining the development and preliminary validation of the questionnaire. Data collected during a pilot study in the Department of Linguistics and Literature at the University of Antwerp were used to perform a reliability analysis. The article will proceed with a discussion of the ways in which the questionnaire can inform teaching practice: on the basis of two case reports, teaching strategies for supporting students' autonomy and sense of self-efficacy will be considered. To conclude, a framework suggesting an approach for developing strategy training based on students' perceived efficacy beliefs for the use of learning strategies is proposed.