Objective To analyze the application effect of scenario simulation nursing based on role adaptation theory in breast cancer patients undergoing chemotherapy.Methods A total of 103 breast cancer patients admitted to Tianjin Cancer Hospital Airport Hospital from February 2024 to May 2025 were collected and randomly divided into a control group(51 patients,receiving conventional care)and an observation group(52 patients,receiving scenario simulation care based on role adaptation theory on the basis of the control group)according to the random number table method.The Mini-Mental Adjustment to Cancer Scale(Mini-Mac-19),psychological resilience score,Strategies Used by People to Promote Health(SUPPH),and Functional Assessment of Cancer Therapy-Breast(FACT-B)of the two groups were compared after 2 weeks of intervention and at discharge,and the chemotherapy tolerance of the two groups was compared.Results After 2 weeks of intervention and at discharge,the positive state scores in the Mini-Mac-19 of the observation group were higher than those of the control group,and the anxiety,helplessness/hopelessness scores of the observation group were lower than those of the control group(P<0.05).After 2 weeks of intervention and at discharge,the scores of psychological resilience,SUPPH and FACT-B in the observation group were higher than those in the control group(P<0.05).The chemotherapy tolerance rate of the observation group was higher than that of the control group(P<0.05).Conclusion Scenario simulation nursing based on the role adaptation theory is beneficial for the role adaptation of breast cancer patients undergoing chemotherapy and improves chemotherapy tolerance.