Research on factors associated with motivation to learn (MtL) is limited, particularly among middle-aged adults and immigrants. This study examines educational attainment, literacy skills, and nativity (foreign-born vs. native-born) as predictors of MtL in middle-aged adults living in the United States. Nationally representative data of middle-aged adults between the ages of 40 and 65 years were obtained from the 2012/2014 Program for International Assessment of Adult Competencies (PIAAC). Structural equation models were used to assess the validity of the latent MtL construct and to examine the associations with the selected determinants in middle-aged adults. Postsecondary education degrees and higher literacy skills were linked with greater MtL. However, foreign-born individuals had lower MtL than their US-born counterparts. Educators and researchers should be aware of lower educational attainment, limited literacy skills, and being an immigrant as possible demoting factors of MtL, and in turn, barriers to lifelong learning participation among middle-aged adults.