Background The Affordable Care Act has the potential to significantly affect access to care for previously uninsured patients in need of emergency general surgical care. Our objective was to determine the relationship between insurance status and disease complexity at presentation among a national sample of emergency general surgical patients. Methods Data from the National Emergency Department Sample from 2006–2009 were queried to identify all patients aged 18–64 years old admitted through the emergency department with a primary diagnosis of appendicitis, diverticulitis, inguinal hernia, or bowel obstruction. Primary outcome of complex presentation was defined as also presenting with generalized peritonitis, intra-abdominal abscess, perforated bowel, intestinal gangrene, or other disease-specific measures of complexity. We used multivariable logistic regression to determine the independent association between insurance status and complex presentation. Models accounted for patient- and hospital-level covariates. Counterfactual models were used to estimate the risk of complex presentation attributable to lack of insurance. Results A total of 1,373,659 patients were included, with an overall uninsured rate of 12.3%. Uninsured patients had significantly higher, unadjusted rates of complex presentation, and uninsured payer status was independently associated with complex presentation (odds ratio 1.38, 95% confidence interval: 1.34–1.42). Counterfactual models suggest that having insurance would result in a 22.37% (95% confidence interval: 22.35–22.39%) relative decline in risk of complex emergency general surgical presentation among the uninsured population. Conclusion Insurance status is independently associated with severity of disease at presentation among emergency general surgical conditions nationally. In light of recently reaffirmed Affordable Care Act insurance expansion provisions, these results anticipate increased timely access to operative care for newly insured patients and a corresponding decline in complex, emergency general surgical presentations.