This exploration reports on English as a foreign language (EFL) learners’ writing anxiety based on an ecological perspective within the framework of nested ecosystem model. The study was conducted on four upper-intermediate EFL learners, aged 14–18. Semi-structured stimulated recall interviews, teacher observation, student journal, and task-motometer were all instrumented over ten classroom sessions to provide information concerning learners’ writing anxiety which were analyzed qualitatively. Along the lines of nested ecosystem model, emerging patterns of learners’ writing anxiety were analyzed under four categories of micro-, meso-, exo-, and macrosystems. Findings of the study proposed adequate decisive evidence supporting the fluctuating trajectories and variables concerning learners’ writing anxiety within the interaction of the individual and environmental factors.