This study examines the underexplored tensions and complementarities between bridging ties and strong ties in innovation-seeking alliances. Bridging ties span structural holes to provide innovation potential but lack integration capacity, and strong ties provide integration capacity but lack innovation potential. We theoretically develop the idea that—notwithstanding their tensions—strong ties complement bridging ties in enhancing alliance ambidexterity at the project level. While bridging ties provide access to diverse, structural hole-spanning perspectives and capabilities, strong ties help integrate them to realize an innovation. We also propose that their effects and complementarities influence alliance ambidexterity because they facilitate knowledge integration at the project level. Tests using data on 42 innovation-seeking project alliances involving a major American services conglomerate and its alliance partners support the majority of the proposed ideas. Implications for interfirm network configuration, strategic alliances, and the broader strategy literature are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.