Objective To explore the relationships among ruminative thinking, moral commitment, moral resilience, and ethical behavior in nurses, and to provide a reference for improving their ethical practices. Methods Clinical nurses from nine Grade A tertiary hospitals in Hunan Province were selected via convenience sampling. A questionnaire survey was conducted using a general information questionnaire, the Ethical Behavior Scale for Nurses-Revise, the Rushton Moral Resilience Scale, the Ruminative Responses Scale, and the Moral Commitment Scale for Nurses. Results A total of 1,661 valid questionnaires were collected. The nurses′ ethical behavior score was (66.99±6.96), which was positively correlated with moral resilience and moral commitment, and negatively correlated with ruminative thinking (all P<0.05). Structural equation model indicated that moral resilience had a direct effect on ethical behavior, and also produced significant indirect effects through ruminative thinking, moral commitment, and their chain pathway (all P<0.05). Conclusion Nurses′ ethical behavior is at a moderate to high level.Ruminative thinking and moral commitment play a chain mediating role between nurses′ moral resilience and ethical behavior. It is recommended that nursing managers strengthen scenario-based ethical training and psychological support to enhance nurses′ ethical resilience, implement mindfulness-based interventions to reduce ruminative thinking, and provide values-based education to promote moral commitment, resulting in boosting the improvement of ethical behavior of clinical nurses.