This research concerns how cross-functional integration can support a project management office (PMO) in achieving its goals in the execution of investment projects. A case study was accomplished in a large state-owned Brazilian enterprise that produces and transmits electric power. The results showed several factors that generate cross-functional integration, such as communication and group spirit support. These factors can generate the following impacts: enhanced control over process development; effectiveness of processes/projects; and standardisation of processes. Research also conceptualised the role of integration inhibitors that end up negatively influencing the joint performance of functional areas, decreasing the support that cross-function integration provides for the operation of a PMO. Moreover, another concept of cross-functional integration that emerged from the case is related to controversies that are integration initiatives generating positive results in parts of the process, but generate dysfunctions in other hierarchical levels or stages of the process.