AbstractUnfinished, rationed, missed, or otherwise undone nursing care is a phenomenon observed across health‐care settings worldwide. Irrespective of differing terminology, it has repeatedly been linked to adverse outcomes for both patients and nursing staff. With growing numbers of publications on the topic, scholars have acknowledged persistent barriers to meaningful comparison across studies, settings, and health‐care systems. The aim of this study was thus to develop a guideline to strengthen transparent reporting in research on unfinished nursing care. An international four‐person steering group led a consensus process including a two‐round online Delphi survey and a workshop with 38 international experts. The study was embedded in the RANCARE COST Action: Rationing Missed Nursing Care: An international and multidimensional Problem. Participation was voluntary. The resulting 40‐item RANCARE guideline provides recommendations for transparent and comprehensive reporting on unfinished nursing care regarding conceptualization, measurement, contextual information, and data analyses. By increasing the transparency and comprehensiveness in reporting of studies on unfinished nursing care, the RANCARE guideline supports efficient use of the research results, for example, allowing researchers and nurses to take purposeful actions, with the goal of improving the safety and quality of health‐care services.