This study uses a framework in line with the expected utility theory in terms of the acceptance of NIMBY facilities to examine the impact of the expression of gratitude by project organizers and beneficiaries toward those afflicted on their acceptance of a project. With a high-level radioactive waste disposal facility, a waste incineration facility, and a highway interchange as the subjects, a vignette experiment operating with the expresser of gratitude and the timing of expression was conducted. The results indicated that when gratitude is well acknowledged, approval for NIMBY projects increases. When avoidance is low and gratitude is well recognized, the effect of gratitude expression increases. Furthermore, when gratitude is expressed early on, approval is increased through trust in the authorities and a sense of social contribution. When gratitude is expressed later, its awareness directly increases approval. Thus, in consensus building for NIMBY projects, it can be said that acceptance of the project is promoted through expressions of gratitude by choosing the appropriate timing and method.