Résumé : Background: Since 2007, integrated care of acute malnutrition has been promoted in Niger, a country affected by high burden of disease. This policy change aimed at strengthening capacity and ownership to manage the condition. Integration was neither defined nor planned but assumed to have been achieved. This paper studied the level and progress of integration of acute malnutrition interventions into key health system functions. Methods: The qualitative study method involved literature searches on acute malnutrition interventions for children under 5 in low-income countries to develop a matrix of integration. Integration indicators defined three levels of integration of acute malnutrition interventions into health system functions - full, partial or none. Indicators of health services and health status were added to describe health system improvements. Data from qualitative and quantitative studies conducted in Niger between 2007 and 2013 were used to measure the indicators for the years under study. Results: Results showed a mosaic of integration levels across key health system functions. Four indicators showed full integration, 22 showed partial integration and three showed no integration. Two-thirds of system functions showed progress in assimilating acute malnutrition interventions, while six persistently stagnated over time. There was variation within and across health system domains, with governance and health information functions scoring highest and financing lowest. Steady improvements were noted in geographic coverage, access and under-5 mortality risk. Conclusions: This study provided useful information to inform policy makers and guide strategic planning to improve integration of acute malnutrition interventions in Niger. The proposed method of assessing the extent of integration and monitoring progress may be adapted and used in Niger and other low-income countries that are integrating or intending to integrate acute malnutrition interventions.