Simple Summary International development organisations have improved billions of human lives in the Global South, but the welfare of animals is not usually "on their radar". This is problematic because their activities often affect animals, either directly (e.g., livestock in their own projects) or indirectly (e.g., advising governments on agriculture policy). Poor welfare standards risk organisations' reputations, particularly with donors; they reduce livestock lifespans and productivity, harming recipients; and they cause animals unnecessary pain and suffering. These guidelines were developed through extensive stakeholder engagement with organisations, donors, and recipients, especially in Africa. In these guidelines, we lay out the basic principles of good animal welfare. This includes sections on appropriate food, housing, veterinary care, transport, and slaughter. We hope that, by adopting these guidelines, international development organisations will promote good animal welfare.Abstract International development organisations have improved billions of human lives in the Global South. However, in both their projects and advice to governments, most of these organisations neglect animal welfare. This blindspot matters. Poor welfare standards risk the organisation's reputation, particularly with donors; they reduce livestock lifespans and productivity, harming recipients; and they cause animals unnecessary pain and suffering. Here, we set out animal welfare guidelines for international development organisations. They were developed through extensive stakeholder engagement with organisations, donors, and recipients, especially in Africa. To comprehensively cover animal welfare, the guidelines encompass governance structure within the organisation, staff training, standard operating procedures, water, food, housing, social isolation, enrichment, drainage and waste disposal, disease, invasive procedures, transport, slaughter, breeds, record-keeping, and monitoring and evaluation of success. We urge international development organisations to adopt and institutionalise these guidelines, so they promote good animal welfare.