Drawing on knowledge-based, organizational learning, and social capital perspectives, we propose and test an integrated framework in which knowledge tacitness and trust act as mediating mechanisms in the relationship between partner characteristics and alliance outcomes. We distinguish between learning and innovation outcomes and suggest that while innovation may result from alliance learning, it can also be created by combining separate knowledge bases without learning from each other. We contend that tacitness and trust play differing roles in the pursuit of learning and innovation and test this proposition on a sample of 120 international strategic alliances.