Influenza and pertussis are the two most common vaccine-preventable infections notified in Australia. We assessed the role of polymerase chain reaction (PCR) diagnosis in influenza and pertussis cases notified to the Australian National Notifiable Diseases Surveillance System (NNDSS). There were a total of 2 10 786 notified influenza cases (2001–2013) and 2 55 866 notified pertussis cases (1991–2013). After 1 January 2007, the majority of influenza and pertussis notifications were PCR-based (80·5% and 59·6%, respectively). Before 31 December 2006, PCR-based notifications were limited (29·1% and 11·7%, respectively). By 2013, PCR-based notifications had largely replaced all other diagnostic methods, with the exception of serology-based notifications in pertussis cases in adults aged ⩾25 years.