Online social networks offer appealing ways for interaction and communication. In recent years, people have become used to receiving, obtaining and sharing a great deal of information or knowledge in this way. However, these apps may also raise concerns about differences between topics or users. Developing a principled understanding of how people assess the credibility of mobile instant messages and share information is a critical stage in this process, which may allow us to determine the whole process of information sharing on mobile instant messaging apps. Given the uniqueness of mobile instant messaging, this study enriches our understanding of why and how credibility evaluation and information sharing matter in mobile instant messaging. Moreover, we studied how prominence and interpretation work together to determine credibility on mobile instant messages and drew on a successive knowledge sharing behavior theoretical model to explain the determinants affecting users’ information sharing intentions.