ABSTRACTOnline product reviews provide vital information to help customers with their purchase decisions. It is therefore critical for administrators of online review websites to ensure the credibility of their sites. Most studies have focused on customers’ perceptions of the source credibility of online review websites before the customers make a purchase. However, the studies have ignored the fact that purchase decision outcomes (i.e., product performance) may also influence the perceived credibility of the source. We address this research gap by considering the perception of source credibility in both the prepurchase and postpurchase phases. We draw upon source credibility theory to define the concept of incongruous source credibility (ISC) in the context of online review websites. This concept is based on a customer’s mental comparison of prepurchase versus postpurchase perceptions of source credibility. Three experimental studies were conducted to investigate the impact of ISC on customers’ revisiting intention and positive word of mouth. The studies explored the moderating effects of message valence and review sidedness as well as the mediating effects of disappointment and satisfaction. The results show that the consistency or inconsistency between the online review and product performance can lead customers to reconsider their judgments of the credibility of online review websites. The results also show that ISC affects both revisiting intention and positive word of mouth for such sites. The findings contribute to research on source credibility and online review websites, suggesting that practitioners managing these sites should consider customers’ ISC.