Mass customization interfaces typically guide consumers through the configuration process in a sequential manner, focusing on one product attribute after the other. What if this standardized customization experience were personalized for consumers on the basis of how they process information? A series of large-scale field and experimental studies, conducted with Western and Eastern consumers, shows that matching the interface to consumers’ culture-specific processing style enhances the effectiveness of mass customization. Specifically, presenting the same information isolated (by attribute) to Western consumers but contextualized (by alternative) to Eastern consumers increases satisfaction with and likelihood of purchasing the configured product, along with the amount of money spent on the product. These positive consumer responses emerge because of an increase in “interface fluency”—consumers’ subjective experience of ease when using the interface. The authors advise firms to personalize the customization experience by employing processing-congruent interfaces across consumer markets.