Cancer is usually accompanied by considerable stress for the sufferer, and the stress has destructive effects on Chemotherapy treatment process. Therefore, the current research deals with the effect of yoga laughter on the cancer patients' stress before chemotherapy.In this research, as the first step, 37 cancer sufferers , who had been hospitalized in Shohada Tajrish Hospital (Behnam Daneshpoor Charity Organization) and had the requirements necessary for being taken as research samples, were selected for data collection. The mentioned patients were classified randomly in experimental and control groups. Collected data were analyzed by the multi-variable covariance analysis test.The results show there is a meaningful difference in the stress average before and after interference in the test group (p<0.05).Laughter yoga can decrease the stress in cancer sufferers before chemotherapy.