OBJECTIVE: To examine the effects of diaphragm breathing relaxation training and cognitive-behavioral therapy on sleep quality in the elderly. METHODS: In this three-arm randomized clinical trial, 99 older patients with a primary diagnosis of insomnia were randomly divided into two intervention groups (n = 33) and a control group (n = 33). The study design was a parallel group trial with an allocation ratio of 1:1. The CBT-I intervention was done in a group format for four weeks, consisting of two 60-min sessions per week. The diaphragmatic breathing intervention was trained in a group setting session and practiced individually for 30 min every night before sleep. The control group received no information about sleep or relaxation. Participants completed the Pittsburgh Sleep Quality Questionnaire before, four weeks, and eight weeks after the intervention. RESULTS: A total of 99 patients were randomized to the CBT-I intervention (n = 33), diaphragmatic breathing intervention (n = 33), or control arm (n = 33), with 74 patients providing final analysis data. Repeated measures ANOVA revealed a significant decrease in sleep quality score (p <
0.001) from pre-test to post-test and one-month follow-ups. The greatest effect of both interventions in reducing the sleep quality score was during the first period of the study (four weeks after the intervention), and there was no significant reduction eight weeks after the intervention. CONCLUSION: Diaphragmatic breathing and CBT-I interventions improved sleep quality indicators among older adults.