Background Nursing students experience a high level of stress in clinical settings. This study aimed to investigate the stress perceived by Iranian nursing students in the clinical learning environment and its relationship with the characteristics of students. Methods In this cross-sectional study, 430 nursing students who had passed at least 1 clinical training unit were recruited from universities in the Southeast of Iran using the census method. Data were collected by administering a demographic and researcher-made questionnaire to assess the perceived clinical stress. Demographic characteristics included age, sex, marital status, year of study, interest in the field, and previous semester average. Data were analyzed using independent t -test, ANOVA, and correlation coefficient test (α < 0.05). Results The mean score of overall stress experienced by the participants was 92.08±16.8 (out of 160), which was at a moderate level. Based on the study results, the most stress-inducing factors for students were instructors’ limited clinical competence and instructors’ inappropriate conduct. Gender (p = 0.01), fathers’ education (p = 0.01), mothers’ education (p = 0.01), interest in the field (p = 0.01), and year of study (p = 0.01) had a significant effect on the mean score of perceived clinical stress. Conclusion The results of this study showed a moderate level of stress among the students. Also, instructors’ limited clinical competence and inappropriate conduct were 2 factors that caused the highest perceived stress among nursing students more than other factors.