BACKGROUND: The Canadian Acute Respiratory Illness and Flu Scale (CARIFS) is a parent-proxy questionnaire that assesses severity of acute respiratory infections in children. The aim was to (a) perform a cross-cultural adaptation and (b) prove that the Malay CARIFS is a reliable tool. FINDINGS: The CARIFS underwent forward and backward translations as recommended by international guidelines. A pilot study was performed on the harmonised version and the final version of the Malay version of CARIFS was produced. A test-retest, 1 h apart, was then performed on parents with children less than 13 years old, admitted with a respiratory tract infection. Parents of children with asthma and who were not eloquent in Malay, were excluded. The data was analysed for consistency (Cronbach's alpha) and reliability (test-retest co-efficient). Thirty-three parents were recruited. Children were aged median (IQR) 6 (2.8, 13.3) months with a male: female ratio of 22:11 and 88% were Malays. Parents were interviewed at median (IQR) 6 (3, 11.5) days of admission. The Cronbach's alpha coefficient was 0.70 for all items. The test-retest reliability analysis had a minimum and maximum intraclass correlation coefficient of 0.63 and 0.97 respectively. Clinically, the longer patients were admitted, the lower the severity score (r = -0.35, p < 0.05), indicating that they were getting better. CONCLUSION: The Malay version of CARIFS is a valid and reliable tool to determine severity of respiratory illness in children. Parent-centred questionnaires are useful and should be an adjunct to other methods, in monitoring response to treatment.