The Environmental, Social, and Governance (ESG) practices have been transformed dramatically, and they no longer constitute the marginal corporate responsibility practices, but rather, they have transformed into core strategic priorities that determine the contemporary organisational competitiveness and legitimacy. In spite of the fact that a considerable bulk of literature evidences an overall positive correlation between ESG involvement and the performance of a firm, the vast majority of empirical studies have been carried out in the context of publicly listed companies and manufacturing industries. Very little academic interest has been given to the case of professional service firms (PSFs), even though they are increasingly important to the economy, and unique in their dependence on relational capital, knowledge intensity and reputational capital. The ESG practices can have an impact on organisational outcomes in PSFs where the quality of service is hard to measure ex ante and the relationships with clients are central, and thus, relational, not operational, efficiencies. To fill this gap, the current conceptual paper creates a synthesised framework on how ESG practices can be converted into organisational performance in the professional service firms under the mediating influence of corporate trust and customer loyalty. This paper is conceptualised using the Resource-Based View, Stakeholder Theory, Signalling Theory, and Relationship Marketing Theory as the ESG represents a strategic intangible resource and credible market signal that increases stakeholder confidence and relationship embeddedness. The suggested model is the next step of the existing literature in that it provides a sequential relational pathway that fits in especially well to a knowledge-intensive service system and provides a theoretical basis of future empirical testing. The paper ends with the theoretical contributions, managerial implications, and future research directions in the emerging ESG services nexus