Context: The COVID-19 pandemic has posed a big challenge to provision of health care. Cancer patients are considered to be at higher risk of developing complications from COVID-19 as they are often immunosuppressed. At the same time, treatment delays and late diagnosis during the pandemic due to travel restrictions, staff shortage, active COVID infections to patients or family members, etc., can lead to tumor progression and poor oncological outcomes. Aims: This retrospective observational study was undertaken to know the effect of the corona pandemic and consequent lockdown on the radiation treatment of oncology patients in our department. Materials and Methods: Subjects of the study were the patients who attended the Oncology Department of Kamineni Academy of Medical Sciences, Hyderabad, which is a tertiary care center, during the COVID-19 pandemic. The study period was 6 months starting from the lockdown on April 24, 2020. Results: In our study, treatment of 16 out of 150 patients (10.67%) was affected due to the lockdown situation consequent to COVID-19 pandemic. Eight patients had treatment interruptions for more than 5 days, six patients discontinued their treatment, and two patients delayed their treatment due to lockdown. Eight patients tested positive for COVID-19 before starting treatment. Out of them, four did not come back for treatment. The mean delay in radiation treatment in the other four patients was 35 days. Two patients had CORAD scores consistent with COVID-19 but were reverse transcription–polymerase chain reaction negative. Two patients turned positive during treatment after which they did not come back. Totally 9.3% (14/150) of the patients' treatment was affected due to corona infection. Conclusions: In our study, almost 20% of the patients' treatment was affected directly or indirectly by the COVID-19 pandemic situation. This in turn may lead to rise in cancer mortality in future.