In an increasingly globalised business environment, it is no longer adequate to analyse and develop supplier-customer relationship portfolios without consideration of a firm's network relationships. While research in business relationships has examined resource allocation and strategy development in the context of a dyadic relationship, portfolios and network relationships, little is known about the network effects of a focal firm's relationships on its performance particularly from both supplier and customer evaluations. The present study attempts to fill this gap by developing a customer portfolio framework that includes four levels of business relationships, and integrates a resource-based view and industry determinants of competitive advantage. The proposed framework is applied and analysed using data of UK-based food service companies. The main results show that a focal relationship performance is influenced by both industry and resource-based advantages in a business network context. The results also suggest that a focal firm can better enhance its competitive position with the knowledge of network effects and interdependence of strategic actions in a business network context.