Background <p>Nursing students often face psychological challenges such as anxiety, depression, and stress, especially when they start their clinical training. These challenges can impair their emotional adjustment and increase psychological distress. Emotional regulation programs may help reduce these negative effects. Therefore, this study aimed to evaluate the effect of an emotional regulation program on emotional adjustment and psychological distress among undergraduate nursing students.</p> Methods <p>This experimental study used a pre-test/post-test design with both an intervention and a control group. A total of 72 fifth-semester nursing students from Razi School of Nursing, Kerman, were recruited using convenience sampling and randomly assigned to the intervention (<i>n</i> = 36) or control (<i>n</i> = 36) group using a lottery method. The intervention group participated in eight sessions of the Gross model-based emotional regulation training. Both groups completed the Emotional Adjustment Measure (EAM) and the Kessler Psychological Distress Scale (K-10) before and one month after the intervention.</p> Results <p>An ANCOVA analysis showed that the intervention group had significantly higher emotional adjustment and significantly lower psychological distress at post-test compared to the control group (<i>p</i> &lt; 0.001). These findings remained significant even after controlling for baseline scores and prior training.</p> Conclusion <p>Emotional regulation training effectively enhanced emotional adjustment and reduced psychological distress among nursing students. Integrating such programs into nursing education may promote mental health and improve clinical performance.</p> Clinical trial number <p>Not applicable.</p>