The perspective in alliance research has shifted from the individual dyad to alliance portfolios; a key descriptor of a firm’s alliance portfolio is diversity. Focusing on firms that are confronted with emerging technological fields, the authors examine the consequences of their alliance portfolio’s technological diversity on superior product innovation. The literature has not been conclusive about the consequences of portfolio diversity. The authors examine the nature of the effect of portfolio diversity on superior product innovation and follow up on the call for a contingency perspective—as not all firms benefit equally from portfolio diversity. The contingency perspective is based on the assertion that a firm’s past strategies in internal knowledge creation are a source of experiences that increase the firm’s capability to leverage extramural knowledge. Theoretically, the study thus contributes to the absorptive capacity literature that has recently acknowledged the importance of such higher-order internal capabilities. By identifying concrete dimensions of internal knowledge creation that enable firms to benefit from portfolio diversity, actionable recommendations are derived on how to align internal knowledge creation with external knowledge sourcing. The empirical support in the biopharmaceutical industry corroborates the developed theory and serves as a warning signal for firms that are ill prepared to leverage a diverse alliance portfolio.