Purpose—This study seeks to identify intra-organisational drivers that enhance the implementation of a purchasing social responsibility (PSR) approach, as well as drivers that influence PSR throughout the phases of the process. Design/methodology/approach—The conceptual framework presents PSR as a process rather than merely a decision. It focuses on three dimensions (centralisation, specialisation, and formalisation) to highlight the role and evolution of key drivers through a three-phase process (setup, operating, and sustaining). The empirical analysis is based on a single qualitative case study of SNCF, France's state-owned railway company, which is particularly advanced in its PSR-related practices. Findings—The intra-organisational drivers differ according to the phase of the PSR process. Transitions across the three phases entail organisational adaptation, which require the company to transform from a mechanistic to an organic structure. Research limitations/implications—This research contributes to a better understanding of the PSR implementation process through an in-depth study focused on intra-organisational drivers. Although relatively understudied, these drivers take important roles. Practical implication—This study identifies operational, intra-organisational leverage actions that can benefit firms that aim to adopt or maintain a PSR approach. It also provides comprehensive guidance for activating these leverages throughout the PSR implementation process, and it helps firms identify their level of PSR. Originality/value—This study proposes the first processual, organisational interpretation of PSR approaches.