The purpose of this study was to examine the shared, direct, and indirect contributions of three metalinguistic skills (phonological awareness, morphological awareness, orthographic knowledge) to the reading comprehension abilities of struggling adult readers. Across studies, these three metalinguistic skills have individually emerged as important predictors of reading comprehension with samples of struggling adult readers. In contrast to research conducted with children, no studies have simultaneously included and examined the shared and direct relations of these metalinguistic skills as well as indirect relations (via decoding and vocabulary knowledge) to adults' reading comprehension skills. The results indicated that the metalinguistic skills, decoding, and oral vocabulary knowledge accounted for 91% of the variance in reading comprehension. A second-order metalinguistic awareness factor, decoding, and oral vocabulary knowledge emerged as uniquely predictive of reading comprehension (1-8.9%). Further, metalinguistic awareness was indirectly related to reading comprehension via decoding and oral vocabulary knowledge. The findings help to develop a more comprehensive model of the underlying component processes involved in adults' reading comprehension skills. The findings may also inform instructional practices and intervention research in adult literacy programs.