Background: Self-medication and misuse of medicines is a growing trend in current society. Objectives:To assess the self-medication practices, misuse of selected oral allopathic medication and associated factors among mothers of children under 12 years attending the outpatient department (OPD) of Colombo South Teaching Hospital (CSTH). Method:A descriptive cross sectional study was carried out among mothers of children under 12 years of age who attended the OPD of CSTH from March to April 2014 on self-medication of selected oral medicines in the preceding six months. Data was collected by a pre-tested intervieweradministered questionnaire and was analysed using SPSS 15.0.Results: Eighty five percent of the 350 study participants were between 25-44 years with a mean age of 33.1±6.7 years. Eighty seven percent of them were Sinhalese, 74% were only educated up to the ordinary level (O/L) and 64% were housewives. There were 54% female children and 51% were between 1-4 years of age. Ninety five percent participants self-medicated their children. There was a statistically significant association between mother's higher education level (p<0.05), unemployed mothers (p<0.01), father's higher education level (p<0.01), father's higher occupational category (p<0.05), increased age of child (p<0.01) and high parity (p<0.05) with selfmedication. Paracetamol was the drug used for self-medication by 92% whilst 8% used salbutamol, amoxicillin and chlorpheniramine. Significant association with misuse of paracetamol was observed among housewives (p<0.01), low educational level of participants and spouse (p <0.05), skilled occupations (p<0.05), older age of child (p<0.001) and having nuclear families (p<0.05). Chlorpheniramine overuse was significantly associated with female child and nuclear family type (p<0.05).Conclusions: Ninety five percent of mothers attending the OPD in CSTH during the study period self-medicated their children. There were statistically significant associations between higher educational level of mothers, unemployed mothers, increasing age of child and increasing number of children with the tendency to self-medicate the child.