BackgroundWith the COVID-19 outbreak in China, the Chinese government took measures to prevent and control the spread of the virus. In-person teaching was replaced by distance learning, which was an unknown challenge for students. In this context, little is known about the perceived distress of nursing students and the relationship between psychological capital, perceived distress, and psychological stress. This study examined the relationship between psychological capital, psychological distress, and perceived stress, and the mediating role of psychological capital in the relationship between perceived stress and psychological distress among nursing students.MethodsThis cross-sectional survey was conducted between January and December 2020 using a convenience sampling method involving 359 undergraduate and specialist nursing students at a tertiary hospital in Shandong Province. Standardised instruments were used to measure psychological capital, psychological stress, and perceived stress. We used SPSS 24.0 and PROCESS macro to analyse the data.ResultsThere was a statistically significant difference in perceived stress among students based on whether they liked the nursing profession (P < 0.01). Relative to nursing college students, undergraduates experienced significantly higher levels of perceived stress (P < 0.01). Nevertheless, there were no significant differences in perceived stress according to gender, place of residence, and being an only child. Psychological distress was positively correlated (r = 0.632, p < 0.001) with perceived stress (r =-0.662, p < 0.001), whereas it was negatively correlated with psychological capital. Psychological capital played a potential mediating role in the relationship between psychological distress and perceived stress.ConclusionsPsychological distress was negatively correlated with psychological capital, and positively correlated with perceived stress. Mediation analyses indicated that psychological capital partially mediated the relationship between perceived stress and psychological distress. Educators should therefore heed students’ perceived stress and develop appropriate mental health counselling programmes for students in the curriculum that could help them reduce their psychological distress. In clinical practice, nursing managers must take effective measures, such as skills training, to improve the psychological capital of nursing students and reduce the negative impact of their psychological distress.