Students with reading disabilities generally know fewer words (breadth) with less in-depth knowledge of those words (depth) than typical students. The present study examined the effects of a "moderately rich vocabulary instruction" in which both breadth and depth of vocabulary are addressed. Nineteen U.S. 4th- and 5th-grade students with reading disabilities learned 12 words in the moderate-encounter condition, where students practiced the target words six times in the context of rich vocabulary instructional activities. The results showed that students with reading disabilities remembered more taught word definitions and understood more sentences that contained taught words than those from the control condition. The findings suggest that providing moderately rich vocabulary instruction with a moderate number of rich vocabulary practices can yield good word learning and sentence comprehension containing target words for students with reading difficulties.