Background Antihistamines are widely prescribed to children but should be used with caution in young children. Objective To determine the paediatric prescribing pattern of antihistamines with a focus on the off-label prescribing and factors that influence such prescribing. Setting Paediatric wards of a tertiary care hospital setting in Malaysia. Methods The pharmacy-based computer system and medical records were used to collect the required data. Labelling status of each antihistamine was determined based on the information provided in the product leaflets. Main outcome measure Antihistamines prescribed off-label and factors associated with such prescribing. Results Of the 176 hospitalised children aged <18 years prescribed with an antihistamine in the year 2012, 60.8 % received it in an off-label manner. Of 292 antihistamine prescription items, 55.5 % were prescribed off-label. Loratadine (35.3 %) was the most frequently prescribed antihistamine and chlorpheniramine maleate (34.0 %) was the most common antihistamine prescribed off-label. The main reason for the off-label prescribing of antihistamines was prescribing at higher than the recommended dose (30.2 %). Binary logistic regression showed that children aged <2 years (OR 12.65; 95 % CI 2.87-55.67) and the number of medications received (OR 1.14; 95 % CI 1.00-1.29) were significant predictors for the off-label prescribing of antihistamines. Conclusion Prescribing antihistamines for children in an off-label manner was prevalent at the studied locations and warrants further investigation on the consequences of such prescribing.