The COVID‐19 outbreak negatively impacted the mental health and emotions of many individuals. The study presented here explores the mental health and emotion regulation experienced by undergraduate nursing students in China during the pandemic. Potential risk factors related to negative mental health symptoms were identified in this study. An online cross‐sectional study including 342 respondents was performed from March 6, 2020, to April 1, 2020, at a University in China. A Generalized Anxiety Disorder‐7 (GAD‐7), Patient Health Questionnaire‐9 (PHQ‐9), and Emotion Regulation Questionnaire (ERQ) were used to evaluate mental health and emotions. The statistical analysis was performed using the Statistical Package for Social Sciences (SPSS) version 22. The prevalence of anxiety, depression, or comorbid anxiety and depression were 55.0%, 56.4%, and 31.6%, respectively. The mean score of cognitive reappraisal and expressive suppression was 29.36 ± 8.00 and 15.55 ± 5.14. Lower scores for cognitive reappraisal and higher scores for expressive suppression were susceptible to symptoms of anxiety, depression, or comorbid anxiety and depression. Issues with mental health occurred in nursing students during the COVID‐19 pandemic. Findings from this study provide a better understanding of the association between mental health and emotion regulation, which will help direct psychological intervention that relieves these issues during the pandemic.