Recent work on SMEs and networks has emphasised the importance of external co-operative ties in enhancing firms' innovative performance. These external ties provide resource constrained SMEs with access to a wider set of technological opportunities through information sharing and resource pooling. Previous studies of the SME innovation-cooperation relationship have used categorical measures to capture tie existence which, while providing some useful insights, largely fail to capture the strength of co-operative relationships and/or the variety of relational directions in which co-operation occurs. This study aims to address this measurement deficiency and explore the SME innovation-cooperation relationship by designing and utilising measures that capture both the multi-scalar (strength) and multi-dimensional (variety) nature of co-operation and innovation. We then apply these measures to a survey of UK manufacturing SMEs. Data is obtained for 371 SMEs, and we then assess the innovation-co-operation relationship within a multivariate regression framework. We find that the strength of cooperative ties across a range of productive activities within the value chain are important facilitators for SME innovative capability; this is true for both product and process innovation. However, we find that SME co-operation with rivals (co-opetition) has no significant impact upon innovation. Our results have significant implications for both supply chain managers and policy-makers interested in enhancing innovation among SMEs. In particular, we argue that SME innovative activity benefits from good, close dyadic relations within the supply chain, while more generally policy should be geared towards nurturing and sustaining SME innovation networks.