PurposeThis research was conducted as a randomized controlled study to examine the effect of breathing exercises on managing chemotherapy-related nausea and vomiting in patients who underwent autologous hematopoietic stem cell transplantation. MethodsA randomized controlled trial design was used, including an intervention group doing breathing exercises and a control group receiving standard care for chemotherapy-induced nausea and vomiting. The sample was selected from patients hospitalized in the bone marrow transplantation unit. A total of 70 autologous hematopoietic stem cell transplantation patients (35 intervention and 35 control participants).Several variables were evaluated, including the frequence and degree of nausea and vomiting, the patient's nutritional status, and the need for antiemetics. Data were analyzed and interpreted using Mann Whitney U, Pearson chi-square test, Independent t-test, Mann Whitney U, and multiple linear regression. ResultsIt was found that there was a negative relationship between the number of breathing exercises, the number of nausea and vomiting and the severity of nausea. As the number of breathing exercises increased, the number nausea and vomiting, and severity of nausea decreased significantly (p < 0.05). It was found that the use of antiemetics decreased in the intervention group. Furthermore, it was found that the intervention group had higher daily food consumption on the 3rd, 7th, and 9th days (p < 0.05). ConclusionBreathing exercises were a practical approach to managing chemotherapy-related nausea and vomiting.