Purpose The current study takes a practical and theoretically grounded look at assessment of morphological knowledge and its potential to deepen understanding of how morphological knowledge supports reading comprehension for students with limited reading vocabulary. Specifically, we explore how different morphological skills support reading comprehension for students with typical reading vocabulary development compared to students with limited reading vocabulary. Method A sample of 1,140 fifth through eighth graders were assessed via a gamified, computer-adaptive measure of language that contained a morphological knowledge assessment. Links to standardized reading comprehension were explored with a focus on determining differences for the 184 students in the sample who showed limited reading vocabulary knowledge. Specifically, multiple regression analyses were used to test for the relation between morphology skills and standardized reading comprehension, as well as the moderator effect of reading vocabulary on the relation between morphological knowledge and standardized reading comprehension. Results Findings indicate that the four instructionally malleable morphological skills identified by the assessment differentially supported reading comprehension. These skills were (a) Morphological Awareness, (b) Syntactic Morphological Knowledge, (c) Semantic Morphological Knowledge, and (d) Phonological/Orthographic Morphological Knowledge. Significant interactions for students with limited reading vocabulary were shown in how the skills of Syntactic Morphological Knowledge, Semantic Morphological Knowledge, and Phonological/Orthographic Morphological Knowledge supported standardized Reading Comprehension. Conclusions Given the challenges students with limited reading vocabulary have with semantic information, Syntactic Morphological Knowledge and Phonological/Orthographic Morphological Knowledge were particularly supportive, suggesting the compensatory role of these morphological skills. In contrast, Semantic Morphological Knowledge had a negative relationship with Reading Comprehension for students with limited reading vocabulary. Implications for theory, research, and practice are discussed.