Introduction: In response to the growing recognition of the importance of the quality care in psychiatric nursing, this study introduces the Psychiatric Nursing Care Quality Questionnaire (PNCQQ) designed to evaluate the quality of care provided to psychiatric patients from diverse cultural backgrounds. Aim: The aim of this research was to develop and validate a comprehensive tool that addresses the unique needs and perceptions of patients across various cultural contexts. Materials and Methods: The development of the PNCQQ involved a rigorous methodology encompassing item generation, expert review, and pilot testing to ensure its relevance and cultural appropriateness. Subsequently, a validation study was conducted with a diverse sample of psychiatric patients to assess the reliability, validity, and cultural sensitivity of the questionnaire. Results: A total of 932 psychiatric patients completed the Psychiatric Nursing Care Quality Questionnaire (PNCQQ) as part of the study. The sample consisted of 57.3% female and 42.7% male participants. The age of participants ranged from 18 to 75 years, with a mean age of 37.8 years. Results indicate robust psychometric properties, including high internal consistency and test-retest reliability, supporting the utility of the PNCQQ in assessing nursing care quality across diverse cultural populations. Conclusions: The implications of this research underscore the importance of culturally competent care in psychiatric nursing practice and highlight the value of utilizing validated instruments to enhance care delivery.