The ability to understand, evaluate, and use written information (literacy), process and communicate mathematical information (numeracy), and access and use digital technology are foundational to full participation in today’s global, knowledge-based societies. This paper employs the 2012 Program for the International Assessment of Adult Competencies (PIAAC) that directly assessed the cognitive skills of adults ages 16 to 65 in 24 OECD2 countries, including the United States. In this report we analyze the U.S. data on English literacy and numeracy among U.S. immigrant adults and explore how their cognitive skills—skills that are tested in English—are related to key immigrant integration outcomes such as employment, income, access to training, and health. Immigrant adults lag U.S.-born adults and account for a large share of U.S. low-skilled adults. Overall, the PIAAC results indicate that U.S. adults fared worse than most of their counterparts across the participating countries in the tested areas of proficiency (i.e., literacy, numeracy, and problem solving in technology-rich environments). The results are significant because research finds that literacy and other cognitive skills are strong predictors of income, employment, education and health and because differences in skill levels are an important source of widening income inequality. We found that immigrants lagged U.S.-born adults in terms of literacy and numeracy in English with both groups scoring below international averages. Immigrants were overrepresented among the low-skilled adults: While immigrants made up 15 percent of the total U.S. adult 16-65 population surveyed by the PIAAC, they accounted for 33 percent of adults with low literacy skills and 24 percent of those with low numeracy skills. Nonetheless we found that despite these relatively low overall scores, immigrants’ impacts on the U.S. overall scores and international standing is minimal.