Purpose: The purpose of this paper is to explain how theories of inter-organizational learning can create new insights and nuances to how processes of intra-organizational learning come about in a single, complex and multi-sited organization. Design/methodology/approach: A constructivist thematic analysis of the "Handbook of Feminist Foreign Policy" produced by the Swedish Ministry of Foreign Affairs (SMFA) is completed, exploring the organization's own presentation of the complex learning processes that took place when implementing the new policy in 2014. Findings: The literature on inter-organizational learning has a so far unexplored explanatory potential to understand learning processes that take place in complex, multi-sited organizations. This case demonstrates why and how this potential is relevant to exploit. Five themes are constructed from the analysis; four pointing out how gender mainstreaming is spread throughout the different parts of the organization and one detailing how the learning process has provided the SMFA knowledge exportable to other organizations. Originality/value: Due to the complexity in large, multi-sited organizations today, this paper argues what is classically understood as solely inter-organizational processes could also apply to a single organization, as the learning processes this engages in, transitions intra- and inter-organizational learning. The study advances current understandings through exploring mechanisms of gender mainstreaming.