Autonomous learning, which emphasizes learners taking charge of their knowledge acquisition, plays a vital role in effective English language acquisition. However, attempts to foster autonomous learning in the Thai context face many challenges. Therefore, this mixed-methods study explores how autonomous learning thrives in the context to inform future attempts to foster autonomous learning. The study employed exploratory sequential mixed-methods research which consists of two phases to collect the data. The data collection began with the qualitative phase which involved interviewing fifteen first-year undergraduate students who have high English language proficiency. The focus was on their English language learning experiences concentrating on the four main constructs suggested by literature to reflect autonomous learning namely: learner beliefs, learning behaviors, metacognitive knowledge, and factors influencing English language learning. Themes and sub-themes emerged from the interview were used subsequently to develop a questionnaire with 396 undergraduate respondents. In the quantitative phase, the questionnaire results confirmed that the findings in the qualitative phase were prevalent in the larger sample. Moreover, the discussion presents several causal relationships between the factors influencing English learning and the other three constructs, suggesting that the manipulation of the factors may help in fostering autonomous learning in the Thai context.