Previous literature has identified sources of customer dissatisfaction in the forms of poor product performance, discrimination, and universal mistreatment (i.e., broad-based mistreatment of customers). This article proposes the existence of a fourth source of perceived customer dissatisfaction, termed transitory bias, which is based upon fleeting customer characteristics and actions. Using a critical incident approach, this exploratory study analyzes customer narratives of 230 negative experiences. After writing their narratives, consumer informants completed a quantitative survey pertaining to their experience. Some sources of transitory bias were found to be customer complaining, negotiation, special requests, and underpurchasing. Transitory bias was found to drive perceptions of negative customer experiences in 29.1 per cent of the narratives. This was fewer than the number of cases involving universal mistreatment (50%) but more than those involving poor product performance (18.3%) and discrimination (2.6%). Results showed that satisfaction, repeat purchase likelihood, recommendation likelihood, and word of mouth were similar to those found in narratives where universal mistreatment and discrimination were primary drivers of dissatisfaction. This article creates awareness of the transitory bias construct and allows academicians the opportunity to study it as a source of customer dissatisfaction. Retail and service establishments should be aware of customer perceptions of transitory bias because it impacts key performance metrics. Managers may wish to train employees to better identify and respond to sources of transitory bias. Copyright © 2013 John Wiley & Sons, Ltd.