Despite their global market presence, mass customization interfaces have typically been developed for Western consumers who process information analytically, attribute by attribute. This emphasis may interfere with Asian consumers’ preference for the holistic processing of contextualized information. A large-scale field study and four cross-cultural experiments show that congruence between the interface and consumers’ culture-specific processing style boosts the effectiveness of mass customization in both Asia and the West, increasing consumers’ satisfaction with and likelihood to purchase a configured product. This effect is driven by the sequential mechanism of (1) greater subjective fluency with the interface and (2) greater subsequent mental simulation of product use. The authors discuss the contribution of this research to mass customization, cross-cultural marketing, and mental simulation and advise firms to use “processing-congruent interfaces” that present the same information isolated (“by-attribute”) to Western consumers but contextualized (“by-alternative”) to Asian consumers.