The aim of this study was, firstly, to explore the development of primary school children’s metacognitive knowledge from preschool to the 2nd grade and the development of their text comprehension skill from the 1st grade to the 3rd grade. Secondly, the developmental dynamics between metacognitive knowledge (MCK) and text comprehension skill (CS) across the first three school years were investigated. The longitudinal sample included 181 children who were tested three times from preschool spring to the spring term of the 3rd grade using an identical set of measurements: the Metacognitive Knowledge Test and Listening and Reading Comprehension Tests. In studying developmental change using Latent Growth Curve modelling (LGC), no uni-construct effect for the development of MCK or for text CS was found. However, a slight multi-construct cumulative development between the children’s MCK and reading CS was identified. Thus, it could be cautiously interpreted that the more the children’s MCK developed from preschool to the end of the 2nd grade, the better reading CS they showed during the first three school years.