PURPOSE: This article describes the evaluation of the implementation of a nursing intervention, that is, the Systematic Activation Method (SAM), among inpatients with late life depression (LLD). METHODS: A qualitative study in four clinical units for old age psychiatry. RESULTS: We identified facilitators and barriers relating to patient and nurse characteristics, as well as to contextual factors, from the perspective of mental health nurses. The nature of the LLD and the quality of the therapeutic relationship were major aspects that affected the implementation of the SAM. PRACTICE IMPLICATIONS: Given the complexity of the implementation process, careful supervision and monitoring, with the active participation of management and the multidisciplinary team, are necessary.