This study examines the impact of live chat on purchase decisions in the context of online outsourcing platforms. A theoretical research model based on signaling theory is proposed. The results of an econometric model based on a unique dataset from a large online outsourcing platform demonstrate that both affective signals (reflected by politeness and sentiment valence) and informative signals (reflected by information quantity and response timeliness) positively affect purchase decisions. In addition, these effects are found to be significantly influenced by consumers' prior experience. Specifically, the findings show that consumers' prior experience undermines the effect of politeness and sentiment valence on purchase decisions, but strengthens the effect of information quantity. In general, this study not only offers a comprehensive understanding of live chat in an outsourcing platform, but also yields insights into how live chat tools can be designed and used to promote online transactions.