This study is a clinical trial aimed to determine the effect of laughter by Katarya method on depression of elderly residing at nursing homes for the elderly and disabled in Rasht city. Sample consisted of 94 elderly patients with mild and moderate depression selected by random sampling method from elderly residing at nursing home. The samples were divided into two groups of experiment (47 patients undergoing laughter therapy program) and control (47 patients with routine care). Inclusion criteria: age 60 years and older, living full-time at nursing home, no history of admittance to psychiatric wards, lack of grief experience during the past six months, residing at nursing home for at least six months, no serious health condition, no surgery in past three month, no history of heart disease, chest pain or open heart surgery, no simultaneous participation in clinical trial, earning depression scale score between 5 and 11, physical ability to participate in the study, interested in participating in the study and signing a consent form. Exclusion criteria: lack of personal interest to participate in any stage of study. Data will be gathered using a 2-part tool consisting of demographic information and geriatric depression questionnaire by interview method. Data will be gathered in two stages of pre intervention and one month after the laughter therapy program. Laughter therapy program by Katarya method will be conducted for 30 minutes twice a week for 5 weeks.