Objectives. Although the treatment of depressive illness aims to restore the imbalance between an excess of negative affect (NA) and a shortage of positive affect (PA), no study has examined how NA and PA may influence each other in depression. This study examines how NA and PA dynamically influence each other in depression and how this may impact on treatment response. Design. Depressed help-seeking individuals participated in the Experience Sampling Method (ESM), which enables visualization of subtle dynamic alterations of momentary affective states over time. Thereafter, participants received a combination of antidepressant treatment and psychotherapy, and were followed up each month. Methods. NA and PA were assessed during ESM at 10 random moments per day for 6 days. Depressive symptoms were assessed at baseline and at monthly intervals during treatment. Results. Future response to treatment was associated with altered baseline NAPA dynamics in individuals with previous depressive episodes. Their daily life boosts of PA were followed by a stronger suppression of NA over subsequent hours than in other depressed groups or controls. Conclusions. Subtle individual differences in daily life emotional dynamics predict future treatment outcome in depression.