Introduction: Reiki is an Integrative and Complementary Health Practice (PICS), recognized and incorporated into the table of procedures of Brazil's Unified Health System (SUS). Objective: To evaluate the effects of applying Reiki in relieving the symptoms of people with advanced cancer who are hospitalized. Methodology: Randomized controlled study, approved by the Research Ethics Committee, to verify the effect of applying Reiki to people with advanced cancer, admitted to a large, highly complex university hospital located in the interior of the state of São Paulo, Brazil. Fourteen participants were selected from the clinical oncology ward and randomly divided into two groups - Reiki and control - with seven participants each. For data collection, an anamnesis was taken, blood pressure and heart rate were measured, saliva was collected to check cortisol levels; the Edmonton Symptom Assessment System (ESAS), Hospital Anxiety and Depression Scale (HAD-S) and Karnofsky Performance Status (KPS) were applied; Reiki was applied for 21 minutes to participants in the Reiki group and, 30 minutes after Reiki, the scales were reapplied and salivary cortisol was collected again. Results: The Mann-Whitney U-test showed a statistically significant difference for the sleep variable (p<0.007) in the intervention group when compared to the control group. Conclusion: The results showed that Reiki improved the sleep of the participants in this randomized controlled trial and demonstrated that, despite the small caseload, the methodology used is valid for studying the impact of Reiki on the symptoms of people with advanced cancer.