The assumption that forms of collaborative working (for example, partnering) can have a substantial beneficial impact on project performance underlies many of the proposed reform agendas in the UK construction sector. The majority of supporting evidence is, however, either anecdotal or limited to individual cases. This shortfall is addressed and aspects of project performance are evaluated relative to different degrees of collaborative working. To achieve this, project performance and collaborative working were first analysed into identified constituents. For clarity, these were referred to as attributes (of collaborative working) and indicators (in the case of project performance). This permitted the operationalization of the two concepts into a more measurable format. Data from 44 projects were evaluated. The results indicate a positive linear relationship between collaborative working and project performance. Further, by seeking associations between these disaggregated attributes (of collaborative working) and indicators (of project performance) a richer picture emerged of how the association between the two headline concepts might possibly be explained. Aside from its theoretical contribution, the work has a practical implication in terms of how project performance might be improved.