The use of digital devices among very young children is quickly spreading, although the effects of screen time on emotional and cognitive functioning are still debated. In a sample of N = 422 children and their mothers, this 4-year longitudinal study aimed to evaluate the hypothesis that the use of digital devices as smartphones and tablets at 4 years of age is related to later dysregulation symptoms and to lower academic achievements both at 6 and 8 years of age. Children's mothers were asked whether or not their offspring had access to digital devices and what was their average screen time on a typical day. Mothers were also requested to specify whether they used to participate in their children's activities during screen time and to report their offspring emotional/behavioral functioning. Children's teachers were administered the Teachers Report Form including the competence part to evaluate academic achievements and possible dysregulation symptoms of their students. The Structural Equation Modeling showed that screen time at 4 years of age, the child was directly, positively and significantly associated with dysregulation and negatively associated with mathematics and literacy grades at 8 years of age of the child. These results could help orientate the guidelines for the use of digital devices by very young children.