Fair resource allocation in humanitarian medicine is gaining in importance and complexity, but remains insufficiently explored. It raises specific issues regarding non-ideal fairness, global solidarity, legitimacy in non-governmental institutions and conflicts of interest. All would benefit from further exploration. We propose that some headway could be made by adapting existing frameworks of procedural fairness for use in humanitarian organizations. Despite the difficulties in applying it to humanitarian medicine, it is possible to partly adapt Daniels and Sabin's ‘Accountability for reasonableness' to this context. This would require: (1) inclusion of internally explicit decisions and rationales; (2) publicity to donors, local staff, community leaders and governments, as well as frank answers to any beneficiary—or potential beneficiary—who asked for clarification of decisions and their rationale; (3) a consistent reasoning strategy to weigh conflicting views of equity in specific situations; (4) advocacy within the organization as a mechanism for revision and appeals; and (5) internal regulation according to publicly accessible mechanisms. Organizations could generate a common corpus of allocation decisions from which to draw in future similar cases. Importantly, the complexity of these challenges should encourage, rather than hinder, broader discussion on ethical aspects of resource allocation in humanitarian medicine.