Purpose - The term customer intimacy has been used both in academia and business, albeit lacking clear definition and empirical validation. The authors in this paper aim to develop a measure of customer intimacy in business-to-business contexts and to assess its reliability and validity, as well as its relevance, within a nomological relationship marketing network. Design/methodology/approach - A multi-method (qualitative/exploratory and quantitative/confirmatory structural modelling), multi-staged (test, re-test) research approach is used and applied in the UK and Germany. Findings - The results show that customer intimacy is a second order construct reflected by the three formative dimensions of mutual understanding, closeness, and value perception. The results also show that customer intimacy is a relevant relationship indicator, distinct from the central relationship indicators of trust and commitment. It impacts relationship commitment levels, customer induced word-of-mouth, repurchase intentions, information disclosure, customer availability, and leads to an advisor status with the customer. Moreover, customer intimacy mediates relationship marketing's central trust commitment link. Research limitations/implications - The main limitations that should be addressed by future studies are: reliance on the key informant technique on one side of the supplier-buyer dyad; cross-sectional design. Practical implications - This study shows that achieving and managing customer intimacy is a relevant managerial goal and task for firms and shows managers how it can be measured and managed. Originality/value. - This study, for the first time, presents a measure for customer intimacy and assesses its quality and impact empirically. The measure will be of significant value in making customer-centric, relationship management approaches more accountable.