In many project-based industries there has recently been an increased tendency for collaboration and co-creation of value with the customers. However, many existing studies report inherent challenges and complexities related to multi-partner collaboration. The paper presents a conceptual framework that explains the focal collaboration-related elements and their interdependencies in multi-partner projects. The elements in the framework and relations between them are derived from the existing empirical studies and theoretical literature on collaboration, knowledge integration and project success. Based on the conceptual analysis of the extant literature we identify eight collaboration antecedents and three collaboration outcome elements. The conceptual framework explains how two collaboration mediators, project collaboration quality and knowledge integration capability, relate collaboration antecedents with collaboration outcomes. In addition, based on the literature analysis we identify 15 mechanisms that enhance the project collaboration quality in multi-partner projects. The article provides novel insights on the dynamics of collaboration in multi-partner projects by offering the concepts of project collaboration quality and knowledge integration capability and explaining their role in collaborative projects.