This study investigates the factors influencing students’ language practices and attitudes toward using English in the Self-Access Learning Center (SALC) at Kanda University of International Studies (KUIS) in a post-pandemic era. Drawing on self-determination theory (SDT) and one of its mini-theories, basic psychological needs (BPN) theory, the research explores how autonomy, relatedness, and competence shape students’ engagement with English in this social learning environment. A qualitative analysis of data collected through interviews with 141 SALC users revealed that while the environment is largely autonomy-supportive and many students value the opportunities to use English, many users lack agency or are satisfied with their relatively limited use of English in the SALC. The results highlight significant barriers that impede the use of English, including the perceived lack of competence, compounded by affective challenges such as feelings of anxiety. In addition, although participants felt a sense of relatedness and regularly interacted with a community of other students in the SALC, the established practice of using Japanese with this group hindered their use of English. The researchers also sought users’ views on the English-only policy on the second floor of the SALC. While the majority of students support the policy in principle, opinions varied on its enforcement, with most advocating for a supportive rather than strict approach. Based on these insights, the researchers recommend maintaining the current policy while enhancing interventions to promote English use, including targeted support systems, linguistic tools, and community-building strategies. These findings contribute to a deeper understanding of how SALCs can better serve diverse learner needs and foster meaningful engagement with the target language.