This paper posits a model of firm–employee relationship strength that permits the future measurement of an index of the strength of intra-firm relationships between the firm and the employees of that firm. The relationship marketing literature currently provides no clear direction as to how to represent and measure the strength of firm–employee relationships. The proposed model emerges from an examination of previous marketing and non-marketing literature through exploration of possible concepts to represent measuring strong and productive work relationships, focusing on relationship strength as the construct of interest. The review of the literature on the concept of relationship strength results in the development of an index model of firm–employee relationship strength predicted by cooperation, balanced power, communication, attachment, shared goals and values, trust and the absence of damaging conflict. The article concludes with a list of contributions that the model provides to the relationship marketing literature, as well as suggestions for future research. This includes examination of the impact of the relationship that a firm has with employees on external firm relationships, most particularly with customers.