PURPOSE COVID-19 caused a disruption in cancer management around the world, resulting in an estimated excess burden secondary to screening disruption and excess lag time for treatment initiation. METHODS We gathered information from primary reimbursement data sets of the public health system of São Paulo, Brazil, from April 2020 to November 2021, and compared these data with those of the pre–COVID-19 period. We used an interrupted time series model to estimate the effect of the COVID-19 pandemic on the rate of key procedures of breast and cervical cancer health care chain. RESULTS We estimated that 1,149,727, 2,693, and 713,616 pap smears, conizations, and mammograms, respectively, were missed or delayed during the COVID-19 pandemic, compared with those in the years immediately before the COVID-19 stay-at-home restrictions. Specifically, we observed an acute decrease of procedures after the COVID-19 stay-at-home restrictions, with a trend to recovery in the long term. Regarding the systemic treatment analysis, we observed a 25% reduction in the rate of initiation of adjuvant systemic treatment for early breast cancer (stage I/II). However, we did not find a clear effect on the other settings of systemic treatment for breast cancer. We estimated an excess of 156 patients starting palliative care for cervical cancer after the COVID-19 stay-at-home restrictions. CONCLUSION The COVID-19 pandemic significantly reduced the performance rate of pap smears, conizations, and mammograms. The initiation of adjuvant treatment for early-stage breast cancer was most susceptible to COVID-19's health system disruption. Furthermore, the downward trend of treatment of advanced cervical cancer was interrupted. Therefore, public health policies are urgently needed to decrease the incidence of advanced cervical and breast cancers caused by delayed diagnosis and treatment initiation. The COVID-19 control policies resulted in reduction of cancer patients' delivery of care. This study evaluated the pandemic's influence in key procedures of breast and cervical cancer chain of care in São Paulo, Brazil. We observed a substantial reduction in the number of mammograms, pap smears, and conizations performed since the onset of the COVID-19 pandemic. In addition, stage I and II breast cancer adjuvant treatment presented a reduced realization rate, whereas palliative treatment delivered for advanced cervical cancer increased. Our results support the need for public health policies focused on mitigating the long-term effects of COVID-19 in cancer-related mortality.