BACKGROUND: Over the past 25 years Sierra Leone has made progress in reducing maternal and child mortality, but the burden of preventable paediatric deaths remains high. Further progress towards achieving the Sustainable Development Goals will require greater strengthening of the health care system, including hospital care for perinatal and paediatric conditions. Emergency Triage Assessment and Treatment Plus (ETAT+) may offer a useful tool. METHODS: The five-day ETAT+ course was adapted as a six-month programme of in-situ training and mentoring integrated with patient flow and service delivery improvements in 14 regional and district government hospitals across the country. Nurses were trained to carry out the initial resuscitation and assessment of the sick paediatric patient, and to administer the first dose of medication per protocol. The course was for all clinical staff; most participants were nurses. RESULTS: The intervention was associated with an improvement in the quality of paediatric care and a reduction in mortality. In 2017 mortality decreased by 33.1%, from 14.5% at baseline to 9.7% after six months of the intervention. Mortality at the start of the 2018 intervention was 8.5% and reduced over six months to 6.5%. Care quality indicators showed improvement across the two intervention periods, with some evidence of sustained effect. CONCLUSIONS: These results suggest that adapted ETAT+ training with in-situ mentoring alongside improved patient flow and service delivery supports improvements in the quality of paediatric care in Sierra Leonean hospitals. ETAT+ may provide an affordable framework for improving the quality of secondary paediatric care in Sierra Leone and a model of nurse-led resuscitation may allow for prompt and timely emergency paediatric care in Sierra Leonean hospitals where there are fewer physicians and other resources for care.