Introduction The COVID-19 pandemic has had a significant impact on healthcare delivery. Although others have documented the impact on new cancer diagnoses, trends in new starts for oncology drugs are less clear. We examined changes in new users of oral oncology medications in the US following COVID-19 stay-at-home orders in 2020 compared to prior years. Methods We examined prescription data for members enrolled with a national pharmacy benefits manager in the US from January 1-October 31 of 2018, 2019, and/or 2020. This is a retrospective, observational study comparing new users per 100,000 members per month for all oral oncology drugs, and separately for breast, lung, and prostate cancer, leukemia, and melanoma oral drugs. We performed a difference-in-differences analysis for change in new users from pre-period (prior to pandemic-induced disruption, January-March), to post-period (following pandemic-induced disruption, April-October), between 2020 and 2019, and 2020 and 2018. Results New oral oncology drug users per 100,000 members per month declined by an additional 11.3% in the 2020 post-period compared to 2019 ( p = 0.048). New oral breast cancer drug starts declined by an additional 14.0% in the 2020 post-period compared to 2019 ( p = 0.040). Similar but non-significant trends were found between 2020 and 2018. No significant differences were found between post-period monthly new starts of leukemia, melanoma, lung or prostate cancer disease-specific oral medications. Conclusions Long-term implications of delays in cancer treatment initiation are unclear, although there is concern that patient outcomes may be negatively impacted.