The study characterized children's literacy, mothers’ beliefs, and writing mediation of homeschooled compared to formally schooled kindergartners. Participants were 60 children (ages 4–6) and their mothers (30 in homeschooling). At the children's home, we assessed children's literacy, maternal beliefs, and video-recorded mother–child joint writing of a birthday invitation. Results showed that homeschooled children had lower literacy levels than those formally schooled. Homeschooling mothers reported lower levels of belief in learning activities and demands from their children and showed lower levels of writing mediation. Maternal writing mediation predicted children's writing, beyond the child's phonological awareness and schooling (home vs. formal).