Objective: This study aimed to evaluate the impact of the coronavirus disease-2019 (COVID-19) pandemic on the follow-up and management of cancer patients. Material and Methods: A survey consisting of 15 questions asking whether there was a delay in followup or treatment of cancer during the COVID-19 pandemic was applied to the cancer patients who were admitted to our medical oncology outpatient clinic for follow-up or treatment. Results: A total of 209 cancer patients were included in this study. In 56 (26.8%) patients, there was a delay in the follow-up or treatment of cancer. The delay in cancer treatment occurred in 37 (66%) patients, and the delay in the follow-up of cancer occurred in 19 (34%) patients. The median delay in the follow-up and treatment of cancer was both 30 days (range 1-120) and (range 2-120), respectively. 12.5% of all patients who encountered delays in cancer follow-up or treatment had subsequent cancer-related complications. Also, the delay was significantly higher in quarantined patients and patients diagnosed with severe acute respiratory syndromecoronavirus- 2. In binary logistic regression analysis, living in rural areas and being quarantined due to the COVID-19 pandemic were determined as independent predictors of the delay. Conclusion: The COVID-19 outbreak caused delays in the follow-up and treatment of cancer patients, and acute complications arose due to unavoidable disruptions. To prevent long-term negative consequences of delays in cancer follow- up and treatment, it is necessary to adapt the treatments judiciously without sacrificing patient safety and care.