Scant research has examined customers as sources of workplace incivility, despite evidence suggesting that mistreatment is more common from organizational outsiders, including customers, than from organizational members (Grandey, Kern, & Frone, 2007; Schat & Kelloway, 2005). As an important step in extending the literature on customer incivility, we conducted two studies to develop and validate a measure of this construct. Study 1 used focus groups of retail and restaurant employees (n = 30) to elicit a list of uncivil customer behaviors, based on which we wrote initial scale items. Study 2 used a correlational survey design (n = 439) to pare down the number of scale items to 10 and to garner reliability and validity evidence for the scale. Exploratory and confirmatory factor analyses show that the scale is unidimensional and distinguishable from measures of the related, but distinct, constructs of interpersonal justice and psychological aggression from customers. Reliability analyses show that the scale is internally consistent. Significant correlations between the scale and individuals' job satisfaction, turnover intentions, and general and job-specific psychological strain provide evidence of criterion-related validity. Hierarchical regression analyses show that the scale significantly predicts three of four organizational and personal strain outcomes over and above a workplace incivility measure adapted for customer incivility, providing some evidence of incremental validity. Limitations and future research directions are discussed.