The resource dependence theory and the resource-based view have been put forward in order to explain inter-firm alliance strategies. According to these approaches, the main driver for alliance formation is the internal resource condition of the firm and the need to acquire external resources. We argue that resource motivation is moderated by perceived environmental uncertainty. First, we conceptualize how perceived environmental uncertainty and resource conditions independently affect the probability of firms to develop alliances strategies. Then, we analyze how the role of resource conditions is affected by environmental uncertainty. Finally, we test our point of view using a sample of Portuguese firms.