OBJECTIVE To evaluate the effects of instrumental sacred music and sacred music with vocals on the spiritual well-being of bereaved relatives. METHOD This is a randomized clinical trial carried out with family members bereaving the death of loved ones to cancer. Participants were allocated into three groups: Group 1 (control), Group 2 (experimental using sacred music with vocals) or Group 3 (experimental using instrumental sacred music). Spiritual well-being was assessed through the Spiritual Well-Being Scale. RESULTS Sixty-nine (69) family members participated. Mean scores before and after the intervention indicated high levels of spiritual well-being (106.4 and 105.5 in Group 1; 103.2 and 105.2 in Group 2; 107.4 and 108.7 in Group 3) and religious well-being (57.9 and 56.9 in Group 1; 56.3 and 56.4 in Group 2; 57.4 and 58.1 in Group 3), and moderate levels of existential well-being (48.5 and 48.6 in Group 1; 46.9 and 48.9 in Group 2; 49.9 and 50.7 in Group 3), with the exception of Group 3 which presented a high level of existential well-being after the intervention. CONCLUSION The results show that there were no statistically significant differences in the spiritual well-being scores between the experimental groups and the control group. We evidence the need for further studies that use music therapy as a Nursing intervention for bereaved families. Brazilian Registry of Clinical Trials: RBR-2wtwjz.