In response to a sharp increase in social network service users, social media have received great attention of marketers as a new communication channel for brand management. Building brand fan-pages on Facebook is a good example. Brand communities on social media enable more interactive communications among the participants compared to other community platforms. Meanwhile, there were few empirical studies that showed unique business values of brand communities on social media. To this end, the current study examined if engaging customers in a brand community on social media is useful for increasing the relationship quality between the customers and the brand. Unlike brand attitude or satisfaction, creating brand attachment requires repetitive good experiences with the brand. Thus, it was hypothesized that customers’ volunteered and continual interactions in a brand fan-page, namely engagement, can also increase their emotional attachment toward the brand. To test our proposed research model, an Internet survey was conducted targeting the users of brand fan-pages on Facebook. Out of 268 responses, 222 valid samples were used for our final analysis after eliminating unresponsive and unreliable responses. This study was interested in the behavioral aspect of customer engagement thus the construct was measured by the level of making posts or comments, sharing brand contents with friends, and participating in brand promotion activities on the target brand fan-page. As the engagement level was measured by its behavioral aspect, common method variance was able to be minimized when testing its relationship with emotional brand attachment. The result of Structural Equation Modeling analysis showed that brand fan-page engagement behaviors had a significant and positive relationship with the level of band attachment(b= .586). According to the result of our multi-group analysis, such relationship was negatively moderated by the level of direct brand experiences (p=.027). It implicates that the role of engagement is more meaningful when consumers don’t have enough brand experience off-line yet. In contrast, the moderating role of self-image congruence was not supported at the five percent level. This study also examined the types of user motivation which facilitate consumer engagement on brand fan-pages. Consumers were hypothesized to use brand fan-pages for information value, hedonic value, monetary benefits such as coupons, self-image presentation, communicate with the brand, and social connection with other fans. The result of our analysis showed that all the types of motivation, except for hedonic value, had significant effect on the engagement behavior. The most important motivation that resulted in customer engagement on fan-pages was the one for two-way communications. In short, consumers seemed to engage more actively in brand fan-pages as they had stronger motivation to share opinions about the brand with other fans and to communicate with the company. The result of this study provides useful implications for practitioners who want to manage brand communities on social media as a useful tool for increasing their brand asset. Creating hedonic contents on brand fan-pages might be able to attract consumers to visit the page in the short-term while our analysis showed that such approach is not effective for making consumers more engaged on the brand community aiming for brand attachment creation. The current study has its unique value in that it is one of the first empirical studies that showed the marketing value of brand communities on social media.