While research on expressive writing (EW) has demonstrated its benefits for depression, relatively few studies have examined its impact on self cognition and emotional state. This case study addresses this gap by exploring how EW alleviates depressive symptoms while reshaping emotional state and self cognition. Drawing on four rounds of EW and six months of follow-up with a university student experiencing severe depression, the findings reveal a moderate but sustained reduction in depressive symptoms, accompanied by marked improvements in emotional balance and self cognition. The student’s trajectory showed a shift from pervasive negative affect to a balanced emotional repertoire, and from entrenched self denial to emerging self acceptance. Importantly, the process was characterized by initial fluctuations, reflecting both rebound effects and cognitive dissonance before stabilization occurred. These results confirm the potential of EW as an effective, low cost intervention for alleviating depression, while also highlighting its role in facilitating identity reconstruction and emotional resilience among college students.