More corporations are recognizing the importance of social media for public relations. However, what communication strategy they should implement on social media remains somewhat unclear in the literature. This study examined the effects of message type and interactivity on a corporate Twitter account. Two types of messages, communal-relationship oriented tweets focusing on consumer relations, and exchange-relationship oriented tweets focusing on sales and product promotion, were tested with either a high or low level of interactivity in a 2 × 2 between-subjects experiment (N = 84). Results indicate that communal messages generated more favorable relationship outcomes such as trust and control mutuality than exchange messages. It was also found that message interactivity positively influenced attitude toward the company, perceived company credibility, and commitment. Implications from both theoretical and practical standpoints are discussed.