The present study was conducted to investigate the effectiveness of child oriented unified protocol for transdiagnostic treatment on sleep disorders and feelings of loneliness in 7- to 11-year-old children with grief experience. The current study was a experimental application with a pre-test-post-test design with a control group and a two-month follow-up period. The statistical population of the study included children aged 7 to 11 who had experienced grief and were studying in Isfahan during the 2024-2025 academic year. In this research, 36 children were selected by purposeful sampling and randomly assigned to experimental and control groups (18 children in the experimental group and 18 children in the control group). The children in the experimental group received the unified protocol for transdiagnostic treatment during ten weeks in ten 75-minute sessions. Children's Grief Questionnaire (CGQ), Children's Loneliness Questionnaire (CLQ) and Child Sleep Disorder Questionnaire (CSDQ) were used in the present study. The data were analyzed through mixed ANOVA via SPSS23 software. The results showed that child oriented unified protocol for transdiagnostic treatment has significant effect on the sleep disorders (p<0.0001) and feelings of loneliness (p<0.0001) in children with grief experience. The current study was a experimental application with a pre-test-post-test design with a control group and a two-month follow-up period. The statistical population of the study included children aged 7 to 11 who had experienced grief and were studying in Isfahan during the 2024-2025 academic year. In this research, 36 children were selected by purposeful sampling and randomly assigned to experimental and control groups (18 children in the experimental group and 18 children in the control group). The children in the experimental group received the unified protocol for transdiagnostic treatment during ten weeks in ten 75-minute sessions. Children's Grief Questionnaire (CGQ), Children's Loneliness Questionnaire (CLQ) and Child Sleep Disorder Questionnaire (CSDQ) were used in the present study. The data were analyzed through mixed ANOVA via SPSS23 software. The results showed that child oriented unified protocol for transdiagnostic treatment has significant effect on the sleep disorders (p<0.0001) and feelings of loneliness (p<0.0001) in children with grief experience.