This study examined factors that affect journalists’ Twitter use behaviors based on the framework of the theory of planned behavior (TPB). A survey of Korean journalists supported that TPB is a useful theoretical framework for understanding journalists’ Twitter use behaviors. This study found that three TPB variables – positive attitudes, subjective norm, and perceived behavioral control – are positively associated with journalists’ general Twitter use (i.e., time spent using Twitter). More importantly, beyond looking at journalists’ general Twitter use, this study expands the literature by distinguishing between expressive Twitter use (e.g., tweeting messages) and consumptive Twitter use (e.g., reading others’ tweets). Results showed that journalists’ attitudes, subjective norms, and perceived behavioral controls were associated differently depending on patterns of expressive and consumptive Twitter usage. Given the role of professional journalists in society, their ways of using Twitter may have a profound impact on the ecology of journalism. Contributing to the literature of the theory of planned behavior by extending its explanatory power to professional journalists’ Twitter usage, the results of this study suggest that future research on journalists’ Twitter use should pay more attention to how Twitter is employed within the journalistic context.