Drawing on an ecological perspective, this paper reports on an investigation into the changes in one first-year college student's beliefs about English teaching and learning since his enrollment. These changes in beliefs are part of the empirical findings of a multiple-case study conducted in the Chinese EFL context. Semi-structured interviews, classroom observations, and learning journals were used to collect data over a period of seven months. Qualitative content analysis with the assistance of the NVivo software was applied to data analysis. The findings revealed substantive changes in this participant's belief systems, mediated by classroom affordances across different situations. This inquiry emphasizes that learners' transition from high school to tertiary study is a critical period, during which their beliefs about second language learning are subject to contextual mediation. The in-depth findings of this inquiry indicate the potential for adopting an ecological theoretical framework to explore the emergent, dynamic, and context-responsive nature of learner beliefs. (Contains 1 figure and 1 table.)