Digital transformation is often discussed as a portfolio of technologies, yet project outcomes depend less on tool acquisition than on the organisation’s capacity to align technology, work design, governance and human judgement. This review develops a socio-technical account of digital transformation as an organisational capability and examines how that capability shapes project management efficiency. A structured integrative review of research published between 2020 and 2025 was undertaken across project management, information systems, operations, organisational change and digital strategy. The synthesis identifies five mutually dependent capability domains: digital architecture, data and analytical discipline, adaptive delivery routines, participative work design, and transformation governance. These domains improve efficiency through faster information flows, shorter decision cycles, earlier risk detection, reduced coordination loss, reusable knowledge and stronger benefits realisation. However, the evidence also shows that digitisation can increase administrative burden, surveillance concerns, fragmented accountability and false confidence when technology is introduced without process redesign or employee participation. The paper proposes an integrated capability framework in which technical affordances generate value only when they are translated through social mechanisms such as role clarity, psychological safety, cross-functional learning and decision rights. Project efficiency is therefore treated as a multidimensional outcome comprising speed, resource productivity, decision quality, adaptability and sustainable value rather than mere schedule compression. The review concludes with a staged operating model, measurable indicators and a research agenda for testing capability configurations across sectors and levels of digital maturity.