During the COVID-19 pandemic, the mode of teaching and learning shifted from mostly offline into the online process. In online learning, interaction and engagement are limited. Thus, it is urgent to prepare students to become autonomous. The activation of students' metacognition is one aspect assumed to be crucial in their learning autonomy. So, this research aimed to describe the relationship between the learning autonomy of good language learners and the activation of their metacognition. This article employed a case study of qualitative design. Thirty participants categorized as autonomous language learners were chosen purposively. They are categorized as autonomous good language learners since they meet the five criteria of autonomous learners by Holec (1981). The data were analyzed through contextual coding. The result shows that 92% of the participant has activated their metacognition. Meanwhile, 8% of participants become autonomous learners without activating their metacognition. This 8% of participants fulfill two of them: orchestrating learning strategies and evaluating learning. Thus, it can be assumed that the activation of metacognition relates to the learning autonomy implemented by good language learners. However, it is not a decisive factor. It needs further study to analyze other learner intrinsic behaviors that probably influence the learning autonomy of good language learners, such as learners' anxiety, motivation, and self-esteem.