Humanitarian interventions are not traditionally associated with diasporas, yet the roles diasporic communities perform during crises often transcend conventional boundaries. Focusing on the war in Ukraine, this paper aims to investigate less-visible humanitarian ecosystems and how diasporic actors coalesced transnationally, the effectiveness and lifespan of such ad hoc responses, as well as implications for the wider humanitarian international community. Drawing upon extensive semi-structured interviews, focus groups and embedded participation, the authors’ proposition is simple: yes, diasporas can perform humanitarian functions, but the effectiveness of such interventions depends on multiple factors, which the research – conducted over eight months (February to September 2022) in Romania, Switzerland, Ukraine and the United Kingdom – aims to highlight. Furthermore, the article examines the networked component of diaspora humanitarian initiatives, zooming in on three sets of interrelated transnational responses (Romanian, Ukrainian and/or stemming from other diasporas) in Switzerland, and the United Kingdom (Northern Ireland, Wales and Greater London).