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Aims and Objectives To explore the process of change within the clinical practice of nurses in mental health inpatient units in the context of a participatory process to improve the nurse–patient therapeutic relationship. Design Participatory Action Research. Methods Ninety‐six nurses from 18 mental health units participated. Data were collected through focus groups and reflective diaries between March 2018 and January 2020. Data were analysed using inductive content analysis. The COREQ guidelines were used. Results The research process was carried out through two cycles of four stages each in which the nurses were able to identify the facilitating and limiting elements of their practice in relation to the therapeutic relationship. They then proposed two consensual improvement strategies for all the units, which they called reserved therapeutic space and postincident analysis. Finally, they implemented and evaluated the two strategies for change. Conclusions This study has shown that, despite the different cultural and structural realities of the participating units, it is possible to implement a collaborative process of change, provided the needs and expectations of both the participants and the organisations are similar. Relevance to Clinical Practice The results obtained through Participatory Action Research were directly transferred to clinical practice, thus having an impact on individual nurses and patients, as well as on the collective dynamics of the teams and aspects related to the management of the units. No Patient or Public Contribution Patient or public input is not directly applicable to this study. Patients were recipients of the changes that were occurring in the nurses as part of their daily clinical practice.

BACKGROUND: The practice environment influences the quality of care and the nursing outcomes achieved in their workplaces. OBJECTIVE: To examine the perception of the clinical practice environment among nurses working in mental health units in the context of their participation in an action research study aimed at improving the nurse–patient relationship. METHOD: An explanatory sequential mixed methods study was designed. The data were collected in three phases in 18 mental health units ( n = 95 nurses). Quantitative data were collected through the Practice Environment Scale of the Nursing Work Index, and qualitative data were collected through reflective diaries and focus groups in the context of participatory action research. RESULTS: The nurses’ assessment of their practice environment shifted from positive to negative. Nurse manager leadership was the aspect that worsened the most. In addition, the perception of their participation in the affairs of the center and nursing foundations for quality of care decreased. The nurses considered it essential to be able to influence decision-making bodies and that the institution should promote a model of care that upholds the therapeutic relationship in actual clinical practice. CONCLUSIONS: Nurses perceived that they should be involved in organizational decisions and required more presence and understanding from managers. Furthermore, nurses stated that institutions should promote nursing foundations for quality of care. This study contributes to understanding how nurses in mental health units perceive their work environment and how it affects the improvement of the nurse–patient relationship in clinical practice.