Relationship marketing and its strategic focus on long-term exchanges is an engrained practice in today’s business-to-business (B2B) environment. B2B relationships are important given the reciprocating benefits they offer to offset the resource-intensive investments necessary for relationship initiation and maintenance. However, the reality of the marketplace shows customer defection rates remain a concern, dark side relationship mechanisms emerge as exchanges persist, and suppliers shirk on investing the effort necessary to service their customers. Research is needed to better understand customer defections and the nuanced assessment of perceived supplier complacency in B2B service relationships. To inform this research agenda, the authors assess depth interviews with 56 executive participants across 35 post-mortem customer defection cases. Findings identify thematic representations of perceived supplier complacency within the customer-supplier service provision (i.e. service complacency), as well as during the sales renewal process (i.e. sales complacency).