What is the role of language in social interaction? What does language bring to social encounters? We argue that language can be conceived of as a tool for interacting minds, enabling especially effective and flexible forms of social coordination, perspective-taking and joint action. In a review of evidence from a broad range of disciplines, we pursue elaborations of the language-as-a-tool metaphor, exploring four ways in which language is employed in facilitation of social interaction. We argue that language dramatically extends the possibility-space for interaction, facilitates the profiling and navigation of joint attentional scenes, enables the sharing of situation models and action plans, and mediates the cultural shaping of interacting minds.