Canadian immigrants can be without health insurance for many reasons but limited data exists regarding uninsured health outcomes. Uninsured Canadian residents were identified in the National Ambulatory Care Reporting System for all visits to emergency departments in Ontario, Canada between 2002/3 and 2010/11 (N = 44,489,750). Frequencies for main diagnoses, severity (triage), and visit disposition were compared. Ambulatory care sensitive conditions were identified in a 10 % subsample. The uninsured (N = 140,730; 0.32 %) were more likely to be diagnosed with mental health (insured: 3.48 %; uninsured: 10.47 %) or obstetric problems (insured: 2.69 %; uninsured: 5.56 %), be triaged into the two most severe categories (insured: 11.2 %; uninsured 15.6 %), leave untreated (insured: 3.1 %; uninsured: 5.4 %), or die (insured: 2.8 %; uninsured: 3.7 %). More ACSC visits were made by uninsured children and youth. Insurance status is associated with more serious health status on arrival to emergency departments and more negative visit outcomes.