Nine experiments tested competing hypotheses regarding nonconscious affective responses to acute social exclusion and how such responses may relate to positive mental health. The results strongly and consistently indicated that acute social exclusion increased nonconscious positive affect. Compared to nonexcluded participants, excluded participants recalled more positive memories from childhood than did accepted participants (Experiment 1), gave greater weight to positive emotion in their judgments of word similarity (Experiments 2 and 3), and completed more ambiguous word stems with happy words (Experiments 4a and 4b). This process was apparently automatic, as participants asked to imagine exclusion overestimated explicit distress and underestimated implicit positivity (Experiment 3). Four final experiments showed that this automatic emotion regulation process was found among participants low (but not high) in depressive symptoms (Experiments 5 and 6) and among participants high (but not low) in self-esteem (Experiments 7 and 8). These findings suggest that acute exclusion sets in motion an automatic emotion regulation process in which positive emotions become highly accessible, which relates to positive mental health.