This paper explores how the Museum of New Zealand Te Papa Tongarewa and Alexander Turnbull Library (a division of the National Library of New Zealand Te Puna Mātauranga o Aotearoa) responded to the outpouring of grief in the wake of the Christchurch terror attacks on 15 March 2019. This case study highlights how both institutions, at the invitation of the Wellington Islamic Centre (through the International Muslim Association of New Zealand) collected the hundreds of tributes left at Kilbirnie Mosque in Wellington. This particular acquisition required a shift from a museological object‐centred approach to an archival approach, enabling us to privilege the integrity of the whole. The authors consider the meanings and impacts of such spontaneous memorials; and discuss both the benefits and limitations of collecting material culture generated by ‘first wave’ responses to mass trauma. This case study also demonstrates what can be achieved through collaboration, drawing on aspects of professional practice and theory from across the GLAM (Galleries, Libraries, Archives and Museums) sector.