Given the widespread popularity of social media, such as Facebook and Twitter, social media is considered as a core business communication tool like the mobile phone and email are today. Hence, it is time to be aware of the importance of its impact at work, and how to use it effectively in order to develop the organization and promote business performance. Most of the researches conducted on using social media focused primarily on the individuals' motivations and the organizations' benefits. In fact, minimal amount of research has been conducted regarding the managers' behavior towards using social media in their internal communication. Therefore, this research applied the theory of planned behavior (TPB) to identify and examine the factors that promote or discourage the behavior of managers regarding the usage of social media in the internal organizational context. The theoretical model was validated in a single cross-sectional empirical study of 204 participants. The data was analyzed using structural equation modeling to test the five hypotheses derived from the TPB on the sector level. Of the 5 hypotheses, only 4 were supported. The results add further evidence that the TPB can be applied in the field of organizational research in order to understand the factors that influence and determine the managers' social media usage behavior.