Diarrhoea is one of the leading causes of childhood morbidity and mortality. Proper knowledge about diarrhoea, healthy dietary practices during a diarrheal episode and correct health-seeking behaviour of the mother are crucial to managing and preventing childhood diarrhoea. The objective of the study was to determine the knowledge and practices regarding diarrhoea among mothers of children under the age of five. This descriptive cross-sectional study was conducted from July to December 2019 in the paediatrics ward, Jalalabad Ragib-Rabeya Medical College Hospital, Sylhet, Bangladesh. A total 200 mothers were enrolled by convenient sampling. Among them, 49% of the mothers considered watery and increasing frequency of stool as diarrhoea while 46.5% of mothers considered only the passage of watery stool as diarrhoea. The majority (36%) of the mothers didn’t know the cause of diarrhoea, while eating mud, dirty food and drinking contaminated water were considered causes of diarrhoea by 35.5% and 33% of the mothers, respectively. Thirsty and dry skin were considered sings of dehydration by 30.5% of the mothers, while 48% of the mothers didn’t know the signs of dehydration. Washing hands (49.5%), cleaning the environment (46%), maintaining personal hygiene (36%), boiling water (15%) and properly covering food (14.5%) were the measures stated by mothers that can prevent diarrhoea. During diarrheal episodes, 55% of the mothers used more fluid, while 40% restricted children’s diet. The majority (67.5%) of the mothers visited registered physicians within 2 days of the onset of diarrhoea, while 37.5% self-medicated. The majority (69.5%) of the mothers knew how to prepare oral rehydration saline correctly. There is inadequate maternal knowledge regarding diarrhoea, its prevention and management. This condition may be improved if mothers were given proper health education regarding diarrhoea. 

Key Words: Diarrhoea, Knowledge, Practice, Under five children.