Research suggests that organizational ambidexterity, an organization's capacity to pursue both exploratory and exploitative activities, is critical to firm innovation and performance. Extant research primarily emphasizes several firm-level informal integration mechanisms, such as creating a common vision and relying on social integration, for integrating structurally ambidextrous units. Research has largely ignored, however, the formal mechanisms by which organizations have integrated such units. In this inductive study, using archival and interview data from organizations in Silicon Valley, we address this gap by identifying the formal integration archetypes that enable core business units to collaborate with new venture units to incubate new businesses. The four integration archetypes that enable collaboration vary along two key dimensions: who initiates new ventures and when collaboration is solicited. We identify formal administrative and resource mechanisms that enable such collaboration. We combine the disparate literatures of temporal and spatial separation of ambidextrous structures, and demonstrate how these must be combined at the business unit and new venture levels of analysis to achieve integration. The practical contribution of this study lies in identifying suitable contexts in which each of these archetypes can be utilized by practitioners for reintegrating new venture projects developed in separate structures. Literature reviewThe theoretical tension between integration and separation dominates the literature on organizational ambidexterity (Tushman and Smith, 2002; O'Reilly Rongxin Roger Chen and Rangapriya Priya Kannan-Narasimhan 268 R&D Management 45, 3, 2015