The convenience and pervasiveness of smartphones have created an environment where teacher-parent communication can be easily fostered through mobile apps. The current study aims to explore the role of instant messaging apps in teacher-parent communication. Social capital and the uses and gratifications theory were used to develop a theoretical model. The survey collected 429 valid questionnaires. The findings show that both bonding and bridging capital have a positive influence on constructs including sociability, entertainment, communicatory utility, and emotion. Entertainment, communicatory utility, and emotion have a positive influence on the willingness to use Line as a teacher-parent communication tool. The implications for the extension of communication theory and practice are discussed in the current study.