This paper evaluates whether ISO certification enables a supplier to become an extended resource in a specific sector. The evaluation consisted of a statistical analysis of data from 90 suppliers to a wind turbine manufacturer. The suppliers were selected, evaluated and audited as extended resources from a resource-based view (RBV). We test the differences that the qualified suppliers exhibit in main ISO processes and we identify specific areas that will improve supplier relationships. We also demonstrate significant differences exist when the level of technology the supplier uses is taken into account. Our results may well be applicable in a wider manufacturing processes context. We determine that ISO certification alone is not enough to cement a positive relationship in an upstream supply chain environment, despite such relationships being crucial to the success of a business, and support the use of a wider sector-specific certification tool that goes beyond ISO certification