Objectives: To describe changes in childhood cancer incidence in Australia, 1983–2015, and to estimate projected incidence to 2035. Design, setting: Population‐based study; analysis of Australian Childhood Cancer Registry data for the 20 547 children under 15 years of age diagnosed with cancer in Australia between 1983 and 2015. Main outcome measures: Incidence rate changes during 1983–2015 were assessed by joinpoint regression, with rates age‐standardised to the 2001 Australian standard population. Incidence projections to 2035 were estimated by age‐period‐cohort modelling. Results: The overall age‐standardised incidence rate of childhood cancer increased by 34% between 1983 and 2015, increasing by 1.2% (95% CI, +0.5% to +1.9%) per annum between 2005 and 2015. During 2011–2015, the mean annual number of children diagnosed with cancer in Australia was 770, an incidence rate of 174 cases (95% CI, 169–180 cases) per million children per year. The incidence of hepatoblastoma (annual percentage change [APC], +2.3%; 95% CI, +0.8% to +3.8%), Burkitt lymphoma (APC, +1.6%; 95% CI, +0.4% to +2.8%), osteosarcoma (APC, +1.1%; 95%, +0.0% to +2.3%), intracranial and intraspinal embryonal tumours (APC, +0.9%; 95% CI, +0.4% to +1.5%), and lymphoid leukaemia (APC, +0.5%; 95% CI, +0.2% to +0.8%) increased significantly across the period 1983–2015. The incidence rate of childhood melanoma fell sharply between 1996 and 2015 (APC, –7.7%; 95% CI, –10% to –4.8%). The overall annual cancer incidence rate is conservatively projected to rise to about 186 cases (95% CI, 175–197 cases) per million children by 2035 (1060 cases per year). Conclusions: The incidence rates of several childhood cancer types steadily increased during 1983–2015. Although the reasons for these rises are largely unknown, our findings provide a foundation for health service planning for meeting the needs of children who will be diagnosed with cancer until 2035.