ObjectiveTo present Australia-wide data on paediatric COVID-19 and multisystem inflammatory syndromes to inform health service provision and vaccination prioritisation.DesignProspective, multicentre cohort study.SettingEight tertiary paediatric hospitals across six Australian states and territories in an established research surveillance network—Paediatric Active Enhanced Disease (PAEDS).ParticipantsAll children aged <19 years with SARS-CoV-2 infection including COVID-19, Paediatric Inflammatory Multisystem Syndrome Temporally Associated with SARS-CoV-2 (PIMS-TS) and Kawasaki-like disease TS infection (KD-TS) treated at a PAEDS site from 24 March 2020 to 31 December 2020.InterventionLaboratory-confirmed SARS-CoV-2 infection.Main outcomeIncidence of severe disease among children with COVID-19, PIMS-TS and KD-TS. We also compared KD epidemiology before and during the COVID-19 pandemic.ResultsAmong 386 children with SARS-CoV-2 infection, 381 (98.7%) had COVID-19 (median 6.3 years (IQR 2.1–12.8),53.3% male) and 5 (1.3%) had multisystem inflammatory syndromes (PIMS-TS, n=4; KD-TS, n=1) (median 7.9 years (IQR 7.8–9.8)). Most children with COVID-19 (n=278; 73%) were Australian-born from jurisdictions with highest community transmission. Comorbidities were present in 72 (18.9%); cardiac and respiratory comorbidities were most common (n=32/72;44%). 37 (9.7%) children with COVID-19 were hospitalised, and two (0.5%) required intensive care. Postinfective inflammatory syndromes (PIMS-TS/KD-TS) were uncommon (n=5; 1.3%), all were hospitalised and three (3/5; 60%) required intensive care management. All children recovered and there were no deaths. KD incidence remained stable during the pandemic compared with prepandemic.ConclusionsMost children with COVID-19 had mild disease. Severe disease was less frequent than reported in high prevalence settings. Preventative strategies, such as vaccination, including children and adolescents, could reduce both the acute and postinfective manifestations of the disease.