This article presents the findings of a theory-based evaluation of the Sierra Leone Free Health Care Initiative (FHCI), using mixed methods. Analytical approaches included time-series analysis of national survey data to examine mortality and morbidity trends, as well as modelling of impact using the Lives Saved Tool and expenditure trend analysis. We find that the FHCI responded to a clear need in Sierra Leone, was well designed to bring about needed changes in the health system to deliver services to the target beneficiaries, and did indeed bring funds and momentum to produce important systemic reforms. However, its ambition was also a risk, and weaknesses in implementation have been evident in a number of core areas, such as drugs supply. We conclude that the FHCI was one important factor contributing to improvements in coverage and equity of coverage of essential services for mothers and children. Modelled cost-effectiveness is high-in the region of US$ 420 to US$ 444 per life year saved. The findings suggest that even-or perhaps especially-in a weak health system, a reform-like fee removal, if tackled in a systematic way, can bring about important health system gains that benefit vulnerable groups in particular.