In studying the antecedents of alliance performance, one stream of research has underscored the alignment between partners' characteristics whereas another has concentrated on relational mechanisms such as mutual trust, relational embeddedness, and relational commitment. We integrate these two perspectives by examining how congruence of the partners' cultures and organizational routines facilitates the emergence of relational mechanisms in non-equity alliances. Our analysis of 420 non-equity alliances in the information technology industry demonstrates how differences in partners' internal task routines undermine relational mechanisms that in turn impact alliance performance. Partners who acknowledge their latent differences can overcome some of these negative consequences. We advance alliance research by studying the performance implications of alliance partners' organizational differences and by demonstrating how these effects are mediated by relational mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.