Background: The present study aimed to assess maternal knowledge, attitudes, and practices regarding the use of oral rehydration salts (ORS) in the treatment of childhood diarrhoea in Malaysia. Methods: A cross-sectional study was conducted between 20 November and 20 December 2018. Mothers in different public places across Kuala Lumpur and Selangor were approached to complete a questionnaire. A non-probability sampling method was used to collect data. Results: A total of 400 mothers participated in the study. All mothers had received a formal education, with 80.2% having a tertiary education. 79.0% of participants managed to correctly define childhood diarrhoea, whereas 24.5% and 61.0% correctly identified all diarrhoea symptoms and the preventive approaches, respectively. However, only 49.0% knew that only treated or boiled water can be used to prepare ORS, while 78.8% were aware of the appropriate indication of ORS. The majority of respondents practice good hygiene when managing a child with diarrhoea. Conclusion: Although mothers are equipped with reasonable knowledge regarding diarrhoea and ORS, certain issues identified in the study are disconcerting, namely the use of untreated water for ORS solution preparation, the inappropriate storage of ORS solution, and a lack of understanding regarding the urgency of ORS use. Hence, education interventions could prove useful in overcoming these false perceptions.