Kindergarteners’ emergent writing serves as an excellent measure of their understanding of the written language and as a good predictor of future reading and writing achievements. This chapter describes a study that examined the development of writing processes through a Vygotskian (1978) perspective. Fifty kindergarteners were recorded in their homes in three situations in a fixed order: (1) writing five words with parental mediation; (2) writing the same words independently; (3) instructing the writing of the same words to a hand puppet. Results demonstrate that there are positive correlations between parents’ writing mediation, children’s private speech while writing, children’s understanding of the writing process as expressed while teaching the puppet, and children’s independent writing level. Beyond this, we found that each of these variables has an independent contribution to children’s writing, with the three variables together predicting 80 % of the variance in children’s independent writing level.