Purpose: Firms face the challenge of working with other firms in their business network so as to increase the value of products and services offered to end customers and consumers. This often requires managers to investing in developing strong and effective business-tobusiness relationships. While an extensive literature examines the different dimensions of successful business-to-business relationships, little research examines how perceived corporate identity is likely to influence market relationships. The paper explores how a buyer and supplier draw on their own identities and the identities of each other in ways that enable them to develop a basis on which to conceptualise and operationalise a strategic sourcing relationship. Specifically, the paper investigates the emergent relationship identity that results from buyer-seller interactions. Methodology/Approach: An in-depth, longitudinal case study of a buyer-supplier relationship which involves an engineering buyer and design services supplier. Findings: The study suggests that the corporate identity of companies involved in a relationship has a prominent role in informing and moulding the relationship. Further, the strategic scope of the analysed business relationship adds to the significance of corporate identity in informing the relationship and, ultimately, the business policy. Finally, a key contribution is the notion of ‘relationship dentity’. Relationship identity conveys the idea that when companies develop a continuous relationship, the relationship itself has a unique identity. Research limitations: The research findings are based on a single case study. Additional research across multiple case studies are needed in order to verify the findings reported. Value of paper: This paper addresses a gap in the literature concerning the areas of the role of corporate identity in business relationship development. The findings are important to research and practice with regard to how companies develop successful business-to-business relationships.