Relatedness between foreign business units and the core business unit of the parent firm is an underlying issue in the process of integration and local responsiveness going on in any international industrial firm. In this process, the character of customer needs is an important indicator of the demand for integration/local responsiveness. This study contributes to the development of the business relatedness concept by exploring the performance impact of degrees of relatedness in two international customer contexts: foreign business units delivering to original equipment manufacturers (OEMs), and units delivering to end-user firms. The study focuses on the impact of product, market, skills and branding relatedness on foreign performance. Perceptual data from 191 units of Swedish firms in Germany, the UK, and the US were used to test hypotheses. The findings show that relatedness between the foreign business unit and the core unit of the parent firm is associated with negative foreign performance. Market relatedness and skills relatedness mean low performance in both customer contexts. Branding relatedness has negative effects in the OEM context, while product relatedness has negative effects in the end-user firm context. The findings implicate that we need to pay attention to the significance of low relatedness and the customer context in international settings in developing the relatedness concept.