Background: Recent advances in oncology treatment present an expanding spectrum of cancer-treatment-related emergencies.Many aspects of healthcare utilization, specifically emergency department (ED) visits, are not well studied in this population. The purpose of this study is to determine (1) what proportion of cancer patients visit the ED with an oncology drug-related side effect and are admitted and (2) what factors impact the probability of inpatient admission among these patients. Methods: This study evaluated ED visits by adult patients undergoing active drug treatment for cancer insured by a large commercial and Medicare health plan in the United States between January 1, 2018, and September 30, 2019. Among cancer-related ED visits, logistic regression was used to determine the marginal effect of demographic and clinical characteristics of patients on acute inpatient admission. Results: There were 39,921 total ED visits among patients undergoing drug treatment for cancer; of these, 76% presented with an oncology drug-related side-effect. 36% of all ED visits resulted in admission, 5% resulted in an observation stay. After adjusting, age was not a significant predictor of inpatient admission. Being male (p < 0.01) and living in urban (p < 0.01) or suburban (p < 0.01) zip codes significantly increased the likelihood of admission. Patients with colorectal (p = 0.019), gastrointestinal (p < 0.01), blood (p < 0.01), lung (p < 0.01), metastatic (p < 0.01) cancers, or Hodgkin’s lymphoma (p < 0.01) had significantly increased risk of admission. Patients with prostate (p < 0.01) cancer had a significantly reduced risk of admission. The primary complaint upon presentation to the ED was the most important predictor of inpatient admission; sepsis, pneumonia, medical complications, white cell disorders, metastatic cancer, and fractures were all associated with a significantly higher (all p < 0.001) risk of admission. Patients with comorbid heart failure (p < 0.001), those taking ulcer medications (p < 0.01), or inflammatory bowel disease (p = 0.03) had a significantly increased risk of admission. Results were consistent regardless of payer (Medicare or commercial health plan). Conclusions: This study identified cancer patients for whom acute inpatient admission from an ED presentation is more likely. Future studies identifying cancer patients who may be at risk of making an ED presentation based on demographic, clinical and disease-related characteristics are needed and may help inform targeted follow up of patients to mitigate potentially avoidable ED presentation and subsequent inpatient admission.