A child’s hospitalization in a pediatric intensive care unit (PICU) is a stressful and suffering situation affecting the parents. This correlational study aims to investigate the predicting factors of parents’ psychological well-being with regard to a critically ill child in the PICU. The participants were 100 parents with a child hospitalized in one of the five PICUs of five tertiary hospitals. The research instruments included the Demographic Recording Form, the Child’s Behavioral and Emotional Responses Scale, the Sense of Coherence Scale-Short Form (SOC-13), Thai Version, the Jalowiec Coping Scale (JCS), the Buddhist Belief Questionnaire, the Modified Version of Social Support Questionnaire, Thai Version, and the Psychological General Well-Being Index (PGWBI). Data were analyzed using descriptive statistics, Pearson’s correlation, Spearman’s rank correlation coefficient, and hierarchical multiple regression. The results of hierarchical multiple regression showed that religious belief, the child's behavioral and emotional responses, sense of coherence, coping, and social support could explain 36 % of the variance in the psychological well-being of parents of a critically ill child. The factors that made significant contributions to the model were religious belief (β = 0.29, p < 0.01), sense of coherence (β = 0.27, p < 0.01), the child’s behavioral and emotional responses (β = -0.24, p < 0.01), social support (β = 0.22, p < 0.05), and coping (β = 0.17, p < 0.05). The results of this study may serve as preliminary information for nurses in planning nursing interventions in order to enhance the psychological well-being of the parents.