This research examines customer engagement in social media (CESM) using a meta-analytic model of 814 effect sizes across 97 studies involving 161,059 respondents. Findings reveal that customer engagement is driven by satisfaction, positive emotions, and trust, but not by commitment. Satisfaction is a stronger predictor of customer engagement in high (vs. low) convenience, B2B (vs. B2C), and Twitter (vs. Facebook and Blogs). Twitter appears twice as likely as other social media platforms to improve customer engagement via satisfaction and positive emotions. Customer engagement is also found to have substantial value for companies, directly impacting firm performance, behavioral intention, and word-of-mouth. Moreover, hedonic consumption yields nearly three times stronger customer engagement to firm performance effects vis-à-vis utilitarian consumption. However, contrary to conventional managerial wisdom, word-of-mouth does not improve firm performance nor does it mediate customer engagement effects on firm performance. Contributions to customer engagement theory, including an embellishment of the customer engagement mechanics definition, and practical implications for managers are discussed.