Access to water, sanitation, and hygiene (WASH) is a global public health problem. The situation is worst in conflict areas, where people are displaced from their usual homes. Household supply of WASH and the incidence of diarrhoeal disease among children during the war in Tigray are not known or documented. The objective of this study was to investigate the sources of drinking water, sanitation and hygiene practices, and the incidence of diarrhoeal diseases among children during the war in Tigray, Ethiopia. A cross—sectional study was conducted to collect data on selected WASH indicators in six zones of Tigray from August 4-20, 2021. Data were collected from a total of 4381 sample households selected by lottery. Descriptive analysis was performed and the analysed data are presented in tables, figures and explanatory notes. Binary logistic regression was performed to examine the relationship between independent and dependent variables. A total of 4381 households from 52 woredas participated in the study. Approximately 67.7% of the study participants reported that they relied on an improved source of drinking water during the war. Coverage of sanitation, hand washing, and menstrual hygiene during the war was reported as 43.9%, 14.5%, and 22.1%, respectively. The prevalence of diarrhoeal diseases among children was 25.5% during the war. Water source, latrine type, solid waste disposal and health extension worker visits were the significant predictors of the likelihood of diarrhoea in children (p< 0.05). The results of the study show that a decrease in services from WASH is associated with a higher prevalence of diarrhoeal disease among children during the war in Tigray. To prevent the high prevalence of diarrhoeal disease among children in war-torn Tigray, Ethiopia, improved access to water and sanitation is recommended. In addition, collaborative efforts are needed to engage health extension workers to provide appropriate promotion and prevention services to war-affected communities in Tigray, Ethiopia. Further comprehensive surveys of households with children over one year of age are recommended to assess access to WASH and the burden of WASH associated diseases.