Our research extends the current knowledge based view on the configuration of alliance portfolios and their deployment in different external knowledge environments. We study these alliance portfolios in a longitudinal sample (1996–2010) for over three thousand firms that operate in a large number of industries in the Netherlands. Our findings indicate that partner type variety and partner type relevance, as different dimensions of partner diversity in alliance portfolios, both have an inverted U‐shaped association with firm innovation performance. However, alliance portfolios characterized by both high partner type variety and high relevance cause inferior innovation performance. Different external knowledge environments, characterized by d...