Introduction: Digital screen media use has significantly grown in all age groups and at an increasingly young age, including toddlers, schoolers, and primary school children. Although there is evidence that excessive early childhood media exposure can lead to several negative developmental outcomes, no systematic review on Problematic Media Use (PMU) of children under 10 years old have been provided. The aim of the present systematic review was to identify (i) the main instruments used to measure children’s PMU across different studies; (ii) the risk and protective factors which might increase or reduce children’s PMU; and (iii) the negative outcomes associated with children’s PMU. Methods: This study was conducted following the systematic review guidelines proposed in the PRISMA statement. A total of 35 studies published between 2012–2022 and with a mean sample age between 0 and 10 years old were ultimately included in this literature review. Results: Use of media for more than 2 h a day, male gender, and higher age increased the risk of developing PMU among children. PMU led to several negative consequences for children’s development and well-being (e.g., more problematic behaviors, sleep problems, higher depressive symptoms, lower emotional intelligence, and lower academic achievements). Children who experienced negative psychological symptoms, a dysfunctional parent–child relationship, and difficulties in school context were more prone to develop PMU. However, an authoritative parenting style and restrictive parental mediation reduced the risk of developing PMU among children. Finally, self-report measures specifically designed to get the younger children’s perspective are still few and not so widely used. Conclusions: Overall, this research field is still in its infancy and needs further investigation. Likely, a dysfunctional family system can lead children to experience emotional distress and negative psychological symptoms, which they try to manage by escaping into the virtual world, thus increasing the risk of developing PMU. As the children’s PMU is closely affected by the family environment, future prevention interventions should target both children and their parents to improve their self-regulatory and mentalizing capabilities, as well as parental mediation strategies and general parenting practices.