Environmental sanitation is one of the main factors causing diarrhea, especially among individuals who live in islamic boarding school. This study aimed to obtain an overview and information about environmental sanitation among female student with diarrhea at Islamic Boarding School X. The variables studied include drinking water quality, toilet conditions, rubbish bin, dormitory space density and Clean and Healthy Living Behavior (PHBS). The research method used was descriptive qualitative with data collection through questionnaires and field observations. The research sample consisted of 99 female students with diarrhea in the period April-May 2025. The results showed that the quality of drinking water was in the very good category with a percentage of 90%, the condition of toilets was in the good category with a percentage of 75%, the condition of rubbish bin was in the very less category with a percentage of 48%, the dormitory space density was in the good category with a percentage of 61%. PHBS on hand washing habits was in the very good category with a percentage of 94%, PHBS on waste disposal habits was in the very good category with a percentage of 78%, PHBS on toilet use habits was in the very good category with a percentage of 100%, and PHBS on snacking behavior was in the very good category with a percentage of 90%. This study concluded that although most aspects of environmental sanitation were in good condition, several aspects that need to be improved, such as drinking water quality, toilet cleanliness conditions, waste management and arrangement of dormitory space density. Recommendations were directed at improving environmental sanitation and increasing PHBS awareness to reduce the incidence of diarrhea in Islamic boarding schools. Keywords: Environmental sanitation, Diarrhea, Islamic boarding schools, Clean and Healthy Living Behavior (PHBS).