Acute kidney injury (AKI) is common and associated with extremely poor outcomes. While strategies to tackle deficiencies in basic care delivery are advocated, robust testing of their effectiveness is also needed. The Tackling AKI study was designed to test whether a complex intervention (consisting of an e-alert, care bundle and education programme) can be successfully implemented across a range of UK hospitals, and whether this will deliver improved patient outcomes. This multicentre, pragmatic clinical trial will employ a cluster randomised stepped wedge design to study this in all adult patients who sustain AKI in the 5 participating hospitals over a 2-year period. The intervention will be supported by a comprehensive change management framework. Data collection will include patient outcomes, process measures and a qualitative assessment of barriers and enablers to implementation. This article describes the rationale and design behind the Tackling AKI study.