Purpose – Managing service brands entails managing a portfolio of brand relationships with customers and non-customers. The paper develops a framework for diagnosing the strength of a service brand colored by a customer-dominant business logic perspective. The paper aims to discuss these issues. Design/methodology/approach – Combining insights from the literature on branding, service, and relationship management, the paper develops a customer-dominant conceptual and methodological approach. Brand strength captures customers' attachment to a brand in terms of their thoughts, feelings, and actions toward the brand. Since brand strength is the configuration of customers' and non-customers' brand relationships, the paper divides the brand relationship into two components – brand connection and purchase status – to compose a brand strength map. Findings – Grounded in customers' accumulated positive and negative experiences, the framework creates a diagnostic picture of the strength of the brand, and an illustrative empirical study demonstrates the mapping procedure's applicability to service brands. Research limitations/implications – The approach is an alternative to a traditional measurement scale development approach. Future studies should explore the framework's adaptability to different contexts, stakeholders, and industries. Practical implications – The distinctive model comprehensively captures the aggregate picture of customers' brand relationships, and the managerially parsimonious framework can be adapted to different service settings. Originality/value – The framework represents a novel diagnostic tool for service companies to explore their brand's strength. The approach is unique because it adopts a customer-dominant perspective. Furthermore, it includes behavior with a relational perspective and negative responses, which reduce overall brand strength.