The current study was designed to understand the development of comprehension monitoring among beginner readers from first to third grade, and to determine the extent to which first graders' comprehension monitoring predicts reading comprehension in grade three. Participants were 113 children (57% female) from four US states who were followed from Grade 1 (M = 7 years, SD = 4 months) to Grade 3 (M = 9 years, SD = 4 months). Measures included decoding, vocabulary, working memory, comprehension monitoring, and reading comprehension. Children's ability to monitor comprehension grew significantly from first to third grade, with a deceleration in growth over time. In addition, comprehension monitoring in Grade 1 made a significant contribution to reading comprehension in Grade 3, even after controlling for decoding, vocabulary, and working memory. Together, these findings supplement our understanding of young readers' development of comprehension monitoring as well as its association with reading comprehension at a later time. Practical implications of the results in the context of providing support for higher-level language skills in beginning reading instruction are discussed.