<p>This study aimed to examine an extended Simple View of Reading Model on Korean students in Grades 1 and 2 time-points, including text reading fluency as an additional component. For students in lower grade levels, especially for languages that have consistent orthographies, a wide array of theories suggest text reading fluency supports reading comprehension. Yet, not many studies have explored this relation longitudinally. We invited 120 first-grade children in Korea to participate in our study on their Grade 1 and Grade 2 time-points. We assessed them on decoding, listening comprehension, text reading fluency, and reading comprehension. We examined the patterns of language and reading-related variables at each time point across the extended reading model using structural equation modeling. At Grade 1, the full mediation model had the best fit, with text reading fluency fully mediating the relation between decoding and reading comprehension. At Grade 2, the partial mediation model had the best fit; as decoding and listening comprehension predicted reading comprehension directly and indirectly via text reading fluency. For both time-points, text reading fluency directly predicted reading comprehension, while decoding predicted reading comprehension only indirectly through text reading fluency. This study demonstrated the important role of text reading fluency in reading development among Korean early elementary students. Text reading fluency served as the full mediator in Grade 1 and a partial mediator in Grade 2, indicating a potential developmental shift in the reading process in this early phase of reading development. These findings expand the Simple View of Reading by emphasizing the necessity of text reading fluency in understanding the complex mechanism of early reading development.</p>