Considering the welfare of animals used in research is crucial for both the validity of the results obtained and for the social acceptance of animal research. In Europe, the majority of the 5,784 primates currently used for scientific purposes are macaques (Macaca fascicularis and M. mulatta). Inadequate housing conditions can lead to various physiological and behavioural alterations that indicate poor welfare and can impact upon the quality of the data collected. Although there are a number of documents that summarise scientific knowledge on welfare issues and describe the basic needs of macaques, a specific and comprehensive welfare evaluation tool is lacking for the two aforementioned species when housed in a research context. The objective of the Primate Welfare INdicators (PWIN) project is to develop a welfare assessment tool for macaques used in scientific research, through the adaptation of the existing AWIN protocol for farm animals. PWIN aims to provide an objective lifelong assessment of macaque welfare, with repeated evaluations taking place not only during studies but also before and after experimental procedures. The tool comprises an evaluation of macaque housing, nutrition, health and behaviour, complemented by behavioural observations using 10-min continuous focal sampling. PWIN will support ethical research practices, facilitate compliance with regulatory requirements, and enhance information transparency during inspections and project authorisation processes. Beyond tool development, this research seeks to encourage laboratory teams, including researchers, caretakers, and veterinarians, to regularly monitor macaque welfare at the individual level. The imperative to enhance animal welfare considerations in scientific research aligns with European legislation and the 3Rs principle. By establishing a versatile, species-specific method, this research aims to improve existing practices and support ethical, sustainable primate research.