Background: Unplanned paediatric hospital readmissions are key indicators of healthcare quality, often reflecting issues in discharge planning and continuity of care. The COVID-19 pandemic significantly disrupted healthcare delivery and utilisation, yet its impact on paediatric readmission patterns in Australia remains unclear. Methods: A 5-year single-centre retrospective cohort study of 21,262 paediatric admissions and unplanned readmissions at a non-tertiary metropolitan Australian hospital between 21 March 2017 and 20 March 2023 was conducted. Admissions up to 20 March 2020 were classified as pre-pandemic, and those from 21 March 2020 as during the COVID-19 pandemic. We analysed patient characteristics, including gender, age, First Nations status, primary diagnosis, and socio-economic status, to identify UHR trends. Results: During the COVID-19 period, total paediatric admissions declined by nearly 30%, and the readmission rate decreased from 7.5% to 4.6% compared with the pre-pandemic period. Across both cohorts, higher readmission rates were observed among male patients, infants aged 0–12 months, and children from more socio-economically advantaged areas. Readmissions among First Nations children and those with communicable diseases declined during the pandemic period. Conclusions: A higher proportion of males and patients under 12 months of age had higher readmission rates across both periods. These findings highlight the need for targeted early intervention, age-specific discharge planning, and strengthened follow-up care for high-risk groups. Further research should extend the study period beyond the pandemic and include larger cohorts to better characterise long-term trends and improve generalisability.