Although there is great interest on the global stage in promoting plant-based diets (PBDs) to achieve some of the Sustainable Development Goals (SDGs), the results of their adoption are unsatisfactory. Academics propose to entangle this effort by addressing the challenges of dissemination of social innovations (SIs). SIs generate different adoption attitudes, some of them related to socio-psychological aspects on the part of potential adopters. This research work aims to better understand the adoption of SIs, such as PBDs, which may induce socio-psychological concerns in potential adopters. In this sense, this research postulates that current perspectives on the dissemination and adoption of SI offer partial insights into understanding the shift to PBD. To overcome these limitations, a holistic process perspective of the adopter’s decision-making to change diet is derived and proposed. An exploratory, abductive, and theory-building effort has been carried out, based on a cross-analysis of three different adopter profiles, with a total of 69 semi-structured interviews. A new model for a comprehensive understanding from the adopter’s perspective on dietary change is outlined with new socio-psychological insights emerging from the adopter’s viewpoint. Additionally, the new model offers renewed opportunities for practitioners in terms of PBD implementation, usage, and policy.