This study aimed to determine the clinical validation of the nursing diagnosis (ND) of "spiritual distress (00066)" and the sensitivity, specificity, likelihood ratio, and predictive value in parents of children with chronic diseases. This cross-sectional study was conducted using the clinical diagnostic validity method proposed by Fehring. The data were collected through structured interviews and using a researcher-made list that included 5 parts of demographic information, parents' opinions about spiritual distress, the researcher's diagnosis, 74 defining characteristics (DCs) of the ND of spiritual distress, and the Spiritual Well-being Questionnaire. Data were analyzed using descriptive statistics as well as sensitivity, specificity, likelihood ratio, and predictive value. The prevalence of diagnosis was 70% in a sample of 120 parents. Out of the 74 DCs, 39 criteria were validated. Questioning meaning of illness and suffering had the highest sensitivity (98.8%), the highest negative predictive value (88.88%), and the lowest negative likelihood ratio (0.05%). Expressing the lack of meaning in life demonstrated the highest specificity (97.22%), the highest positive predictive value (98.33%), and the highest positive likelihood ratio (25.26%). Parents who search for meaning of illness and suffering related to a lack of meaning in life are in spiritual distress. The ND was validated. These findings can empower clinical nurses to confidently assess and identify patients experiencing spiritual distress, bridging the gaps caused by the absence of standardized tools for assessing spiritual distress in the inpatient setting.