BACKGROUND The 30-item nurses' observation scale for inpatient evaluation (NOSIE-30) developed for the behavioral and observational rating of psychiatric inpatients. OBJECTIVE The purpose of this study was to evaluate the validation of the NOSIE-30 and mental health-care promotion. METHODS The participants with psychiatric disorders were selected from 310 inpatients referred to the military educational hospital in Iran. This study was carried out in two phases: First, translation of the NOSIE-30 into Persian followed the stepwise, iterative procedures developed by the International Quality of Life Assessment project approach. Second, face validity, criterion-related validity and construct validity, and reliability of the Persian version were determined. The concurrent validity was assessed by using the global assessment of functioning (GAF) instrument. Data were analyzed with the SPSS software of version 22. Exploratory factor analysis, the Cronbach's alpha coefficient, and interrater agreement with intraclass correlation coefficient and Pearson's correlation coefficient were used to data analysis. RESULTS Pearson's correlation coefficient between the NOSIE and GAF was 0.75. The interrater reliability for subscale scores and structure of the NOSIE were ranging from 0.70 to 0.94 and Cohen's kappa = 0.74. Furthermore, the internal consistency of the scale's total scores was estimated by Cronbach's alpha = 0.85. CONCLUSIONS The finding indicated that NOSIE-30 Persian version scale has the desirable validity and reliability for evaluating the nursing care of inpatients. Thus, nurses can promote mental health care by applying this scale in the psychiatric setting.