As US policy makers tackle immigration reform, knowing whether immigrants are a burden on the nation’s health care system can inform the debate. Previous studies have indicated that immigrants contribute more to Medicare than they receive in benefits but have not examined whether the roughly 50 percent of immigrants with private coverage provide a similar subsidy or even drain health care resources. Using nationally representative data, we found that immigrants accounted for 12.6 percent of premiums paid to private insurers in 2014, but only 9.1 percent of insurer expenditures. Immigrants’ annual premiums exceeded their care expenditures by $1,123 per enrollee (for a total of $24.7 billion), which offsets a deficit of $163 per US-born enrollee. Their net subsidy persisted even after ten years of US residence. In 2008–14, the surplus premiums of immigrants totaled $174.4 billion. These findings suggest that policies curtailing immigration could reduce the numbers of “actuarially desirable” people with private insurance, thereby weakening the risk pool.