With the aging of the population and the growing prevalence of dementia, specialized and collaborative nursing care is paramount in this area. To ensure better quality care, it is necessary to use effective and context-specific processes to implement evidence-based practices and more specifically clinical nursing assessment. This study aimed to identify and describe factors that may influence the implementation of clinical nursing assessment in mental health care for older people. The Consolidated Framework for Implementation Research was employed to guide evaluation in the pre-implementation phase in the specific context of mental health care for older people. Using a multimethod approach, interviews, focus groups, and a quantitative survey were conducted with a non-probability convenience sample. A total of 39 hospital nurses (registered nurses and head nurses) were interviewed. Analysis yielded five main factors, notably three barriers and two facilitators. Barriers include a lack of general nursing culture, deficiencies in leadership, and difficulties in communication and collaboration. Facilitators comprise team cohesion and the perceived benefits of the study.