To explore emergency department (ED) visits by adults with cancer and to estimate associations between inpatient admissions through the ED and mortality with sociodemographic and clinical factors within this cohort. We conducted a retrospective, pooled, cross-sectional analysis of the Healthcare Cost and Utilization State Emergency Department Databases and State Inpatient Databases for Maryland and New York from January 2013 to December 2017. We examined inpatient admissions through the ED and mortality using frequencies. Among patients with cancer, multivariable regressions were used to estimate sociodemographic and clinical factors associated with inpatient admissions and outpatient ED and inpatient mortality overall. Among 22.7 million adult ED users, 1.3 million (5.7%) had at least one cancer-related diagnosis. ED visit rates per 100,000 population increased annually throughout the study period for patients with cancer and were 9.9% higher in 2017 compared with 2013 (2013: 303.5; 2017: 333.6). Having at least one inpatient admission (68.7% v 20.5%; P < .001) and inpatient or ED mortality (6.5% v 1.0%; P < .001) were higher among ED users with cancer compared with those without. Among patients with cancer, being uninsured (adjusted odds ratio, 0.52; 95% CI, 0.44 to 0.62) compared with having Medicare coverage and non-Hispanic Black (adjusted odds ratio, 0.86; 95% CI, 0.80 to 0.92) compared with non-Hispanic White were associated with decreased odds of inpatient admissions. In contrast, patients with cancer without health insurance, non-Hispanic Black patients, and residents of nonlarge metropolitan areas and of areas with lower household incomes had increased odds of mortality. High inpatient admissions through the ED and mortality among adult patients with cancer, coupled with an increase in cancer-related ED visit rates and observed disparities in outcomes, highlight the need to improve access to oncologic services to contain ED use and improve care for patients with cancer.