INTRODUCTION: The COVID-19 pandemic is driving unprecedented changes in healthcare services worldwide. This study aimed to quantify the impact of the first wave of the COVID-19 pandemic on diagnostic imaging services in Australia using an interrupted time series model. METHODS: Monthly data were extracted from the Australian Medicare Benefits Schedule for all diagnostic imaging services performed between January 2016 and December 2019. Holt-Winters forecasting models were developed for total imaging services as well as for each imaging modality. The models were used to predict monthly data between January 2020 and June 2020 with a 95% confidence interval (P < 0.05). Absolute and percentage residual differences (RD) between observed and predicted services for this time period were calculated. RESULTS: There were statistically significant reductions in total imaging services performed in March 2020 (RD: -332260, -13.1%, 95% CI: -17.5% to -8.4%), April 2020 (RD: -716957, -32.4%, 95% CI: -36.2% to -28.1%) and May 2020 (RD: -571634, -21.4%, 95% CI: -25.1% to -17.3%). Nuclear medicine and CT services were relatively less impacted than general radiography, ultrasound, and MRI services. There was also a statistically significant increase in nuclear medicine and CT services performed in June 2020 compared to predicted values. CONCLUSIONS: During the first wave of COVID-19 in Australia, there was a significant reduction in total diagnostic imaging services, with variable impacts on different imaging modalities. These findings may have significant public health implications and can be used to inform evidence-based strategies in the recovery phase of the pandemic.