The purpose of this paper is to identity the consumer-based antecedents of online Consumer Engagement Behavior (online-CEB). CEB refers to non-transactional behavior focusing on brands, products or firms, with a direct or indirect impact on firm performance. In an interconnected world, non-transactional consumer behavior is likely to become more relevant. Consumers nowadays are much more empowered than before due to their almost unlimited access of information. Social media websites such as Facebook, YouTube and Twitter provide unlimited means for consumers to interact, express, share and create content about products or brands. Thus, firms that ignore non­ transactional behavior may lose opportunities and suffer from negative reputation effects (Kumar et al., 2010; Rust, Lemon, and Zeithaml, 2004). Furthermore, by ignoring non­ transactional behavior, a firm may calculate returns on marketing activities inaccurately (Rust, Lemon, and Zeithaml, 2004).Non-transactional consumer acts such as e-WOM, online product reviews, or product­ related weblogs indicate consumers' online engagement with specific brands, products or firms, and are therefore likely to directly or indirectly impact fims (Muntinga et al., 2011). Verhoef, van Doom, and Dorotic (2007) suggest that understanding and managing online-CEB is an inlportant practice to maximize the value of a firm's customer. A recent study by Brodie eta!. (2011) indicates that consumer engagement enhances loyalty and satisfaction, empowerment, connection, emotional bonding, trust and commitment. Therefore, firms must examine the antecedents of CEB, specifically in online context due to the rise of social networking sites, in order to understand its nature and manage it appropriately.This study begins by reviewing the existing literature on online-CEB and contributes to knowledge by identifying and hypothesising the relationships between the consumer­ based antecedents of online CEB. A conceptual model is developed and an empirical research has been carried out. The samples of this study were collected through online survey, and the data analysis was conducted using the Structural Equation Modelling. The result of this study identifies four relational concepts as the consumer-based antecedents of online-CEB, including consumer product involvement, consumer brand attitude, emotion toward a brand, and brand attachment.