Reciprocating smiles is important for maintaining social bonds as it both signals affiliative intent and elicits affiliative responses. Feelings of social exclusion may increase mimicry as a means to regulate affiliative bonds with others. In this study, we examined whether feelings of exclusion lead people to selectively reciprocate the facial expressions of more affiliative-looking people. Participants first wrote about either a time they were excluded or a neutral event. They then classified 20 smiles–half spontaneous smiles and half posed. Facial electromyography recorded smile muscle activity. Excluded participants distinguished the two smile types better than controls. Excluded participants also showed greater zygomaticus major (mouth smiling) activity toward enjoyment smiles compared to posed smiles; control participants did not. Orbicularis oculi (eye crinkle) activity matched that of the smile type viewed, but did not vary by exclusion condition. Affiliative social regulation is discussed as a possible explanation for these effects.