This study examines young English readers' ability to infer word meanings in context and to use metacognitive knowledge for constructing word meanings in relation to their reading performance. The participants were 61 fourth-grade students in the United States, comprising 24 monolingual English-speaking (ME) students and 37 English-as-a-second-language (L2) students; each group was also divided into strong and emergent readers in English. Participants were asked to read aloud paragraphs containing words unfamiliar to them in two different contextual conditions (i.e., explicit and implicit conditions), to guess the unfamiliar word meanings, and to tell a teacher how they arrived at the inferred meanings. Quantitative analyses found significant differences between strong and emergent readers in their oral fluency as well as in their ability to infer word meanings and articulate their use of metacognitive knowledge. Although significant differences were found in the ability to infer word meanings and the use of metacognitive reasoning between ME and L2 students, such differences disappeared after controlling for the size of students' receptive vocabulary. Qualitative analyses also revealed differences in the kinds of knowledge and strategies that strong and emergent readers relied on when constructing the meaning of unknown words in both explicit and implicit contexts.