Background: Sleep disorders and anorexia are the most commonly reported symptoms of cancer children undergoing chemotherapy. The present study was aimed to investigate the effect of Benson's Relaxation Response (BRR) on sleep quality and anorexia of cancer children undergoing chemotherapy. A quasi-experimental research design was conducted at the pediatric oncology unit of South Egypt Cancer Institute, Assiut University. A total of 80 children took part in this trial, which was randomly divided into two groups: intervention and control. The data was collected using three tools. Tool I: Biosocial demographic characteristics of studied children, Tool II: St. Mary's Hospital Sleep Questionnaire (SMHSQ). Tool III: It included two parts: Part (1) visual analog appetite scale and Part (2) is the functional assessment of anorexia-cachexia therapy (FAACT). The results of this study showed a significant improvement in the sleep quality and anorexia level in the intervention group with a p-value of 0.001, while there was no statistically significant difference in the control group. The researchers concluded that Benson's Relaxation Response had a positive effect on sleep quality and anorexia in cancer children undergoing chemotherapy. For children with cancer receiving chemotherapy, hospitals are recommended to utilize the BRR in conjunction with other therapies to enhance sleep and reduce anorexia.