This study aimed to quantify changes in paediatric injury-related Emergency Department (ED) presentations at a large metropolitan paediatric hospital during the first two years of the COVID-19 pandemic (i.e., 2020 and 2021). This retrospective cohort study included children aged ≤15 years who presented to the ED at the Children’s Hospital at Westmead, Sydney, New South Wales, Australia, with a principal diagnosis of injury during 1 January 2010 to 31 December 2021. Annual and monthly incidence of paediatric injury-related ED presentations from 2010 to 2019 were used to fit autoregressive integrated moving average models, from which forecast estimates with 95% prediction intervals were derived and compared against corresponding observed values to obtain estimates of absolute and relative forecast errors. The distributions of injuries by injury severity in 2020 and 2021 were compared against the 2010–2019 reference period. The annual incidence of paediatric injury-related ED presentations was 7.6% and 4.7% lower than forecasted in 2020 and 2021, respectively, equating to an estimated total of 1683 fewer paediatric injury-related ED presentations during the two-year period. The largest reductions in monthly incidence of paediatric injury-related ED presentations were observed during the periods of major societal restrictions (i.e., March–May 2020 and July–October 2021). Significant reductions in monthly incidence of injury-related ED presentations were observed for minor injuries only, with no discernable reductions in moderate and serious injuries. These findings highlight the impact of the COVID-19 pandemic on paediatric injury-related ED presentations and the need for future epidemiological studies examining secular trends in paediatric trauma volumes to account for the impact of the COVID-19 pandemic.