This study aimed to evaluate the effect of the spiritual support intervention on spirituality and the clinical parameters of women who have undergone mastectomy. This is a pilot study of a randomized clinical trial. The spiritual support intervention was composed of meditation, guided imagery, music, and respiratory relaxation. The outcomes were: spirituality, blood pressure, heart rate, and oxygen saturation. A total of 27 patients were recruited for the study (intervention group, n = 13; control group, n = 14) (Clinical Trials: NCT 01866670/CAE: 00896312.0.0000.5393). The intervention helped patients with breast cancer to increase expression of their spirituality (p = 0.040) and it also decreased heart rate on the first (p = 0.038) and third day (p = 0.017). There was a difference in oxygen saturation on the second day in the control group (p = 0.039). Patients reported that their participation in the research was positive. This intervention had an effect on the sample of women who had undergone mastectomy.