Background and aims: Aging is increasing rapidly both in Iran and across the world. One of today’s challenges is the need for psychotherapy and improvement of mental health among the elderly. Therefore, a way should be sought out for improving happiness, especially among the elderly. This study was aimed to investigate the effect of music on the happiness of the elderly residing at the retirement homes in Kermanshah, west Iran in 2019. Methods: The population of this empirical study of pretest-posttest design including an intervention group and a control group, consisted of all elderly people residing at the retirement homes across Kermanshah in 2019. Participants were selected based on inclusion criteria using convenience sampling and then randomly assigned to intervention group (n: 31) and control group (n: 31). To collect data, the Oxford Happiness Questionnaire (OHQ) was administered to both groups. Afterwards pieces of Kurdish folk and Arnd Stein’s relaxing music authorized by the Ministry of Culture and Islamic Guidance were played for the intervention group through three 45-50-minute sessions per week, and the control group continued their daily activities as before. After one month, the posttest was administered to both groups. Data were analyzed by paired t test and covariance analysis run in SPSS software. Results: The results demonstrated that after a period of music therapy, there was a significant difference in happiness and its dimensions between the two groups. The mean±standard deviation score of happiness was 74.16±10.32 at pretest and 96.90±5.42 at posttest. Mean life satisfaction score was 19.35±4.62 at pretest and 27.48±2.41 at posttest. Mean self-esteem score was 17.77±2.87 at pretest and 23.16±1.81 at posttest. Mean Subjective well-being score was 12.94±1.57 at pretest and 15.35±1.40 at posttest. Mean satisfaction score was 10.94±2.11 at pretest and 13.16±1.59 at posttest, and mean positive mood score was 13.16±2.16 at pretest and 17.74±1.06 at posttest. The paired t test results showed that the mean score of elderlies residing in Kermanshah retirement homes improved after a music therapy program in terms of happiness dimensions including life satisfaction (P<0.001), self-esteem (P<0.001), subjective well-being (P<0.001), satisfaction (P<0.001), and positive mood (P<0.001). Conclusion: This study demonstrated that music improved happiness in the elderly at retirement homes. Thus, we can use music as a non-medicinal, inexpensive tool for enhancement of happiness along with other therapies at retirement homes and hospitals.