Inferencing skills uniquely contribute to the reading comprehension skills of older grade-school and college students. Evidence also suggests that children's reading component skills, such as decoding and language comprehension, differentially contribute to various reading comprehension assessments. However, additional research is needed to investigate the complex relations of foundational reading skills and inferencing skills to sentence-level and passage-level reading comprehension assessments with struggling adult readers. This study examined the relations between struggling adult readers' (N = 125) text-based (decoding, fluency), language based (morphological awareness, vocabulary, language comprehension), and inferencing skills. The indirect effects of language-based reading component skills to sentence-level and passage-level reading comprehension measures through inferencing were also examined. Vocabulary and morphological awareness indirectly predicted passage-level reading comprehension through inferencing. Word reading fluency and vocabulary knowledge uniquely predicted sentence-level comprehension whereas inferencing skills predicted passage-level comprehension. These results suggest that inferencing is an important contributor to the reading comprehension skills of struggling adult readers. These findings also emphasize a need for multiple measures of comprehension to understand the complexity and underlying component processes involved in struggling adults' reading comprehension skills. Educational implications for adult literacy programs are discussed.