Background. Antibiotics overuse is common and is the major cause of antibiotic resistance. Rational use of antibiotics by GPs is essential as most health problems are exclusively dealt within primary care. Postgraduate family medicine (FM) training has become established in various countries over the last few decades but little is known about the effect of FM training on antibiotic prescribing. Objective. To determine whether GPs with FM training prescribe less antibiotics than those without training. Methods. GPs working in a pluralistic primary health care system took part in the 2007–08 primary care morbidity and management survey in Hong Kong and collected information of all consecutive patient encounters during predetermined weeks of data collection. Characteristics of GPs, training status, patient morbidity and antibiotic prescribing pattern were compared using multivariate regression analyses. Results. One hundred and nine GPs, of whom 67 had FM training, participated in the study and recorded 69 973 health problems. The overall antibiotic prescribing rate was 8.5% and that of GPs with FM training was 5.4% compared with the 13.3% among those without. Multivariate logistic regression showed that GPs with FM training were less likely to prescribe antibiotics (odds ratio 0.68, P < 0.05). They had lower antibiotic prescribing rates when managing upper respiratory tract infections, acute bronchitis and cough but higher in treating infective conjunctivitis and acute laryngitis. Conclusions. Postgraduate FM training in Hong Kong is associated with significantly lower antibiotic prescribing rates. This supports the importance of FM training in rationalizing the use of antibiotics in Hong Kong.