Abstract: ProArt is a co-designed humanization programme that uses artistic activities and environmental transformation to enhance the experience of patients and families in a palliative care unit. This study evaluates its social impact through a Social Return on Investment (SROI) approach including patients, relatives, professionals and volunteers. The programme generated measurable improvements in emotional well-being, communication, personal relationships and the overall care environment, as reported by all stakeholder groups. The total social value created amounted to €1,076,855.42 compared with an investment of €129,405.78, yielding an SROI of €8.32 for each €1 invested. A comprehensive sensitivity analysis varying proxy values and attribution parameters confirmed the robustness of the findings, with SROI ratios ranging from €6.51 to €10.64. These results indicate that art-based humanization strategies can deliver substantial social value in palliative care and may represent an effective approach to improving the quality of end-of-life care.