This study identifies differences in health insurance predictors and investigates the main reported reasons for lacking health insurance coverage between short‐stayed (≤10 years) and long‐stayed (>10 years) US immigrant adults to parse the possible consequences of the Affordable Care Act among immigrants by length of stay and documentation status. Foreign‐born adults (18‐64 years of age) from the 2009 California Health Interview Survey are the study population. Health insurance coverage predictors and the main reasons for being uninsured are compared across cohorts and by documentation status. A logistic‐regression two‐part multivariate model is used to adjust for confounding factors. The analyses determine that legal status is a strong health insurance predictor, particularly among long‐stayed undocumented immigrants. Immigration status is the main reported reason for lacking health insurance. Although long‐stayed documented immigrants are likely to benefit from the Affordable Care Act implementation, undocumented immigrants and short‐stayed documented immigrants may encounter difficulties getting health insurance coverage. Copyright © 2013 John Wiley & Sons, Ltd.