Problematic media use in children and adolescents has been linked to various mental health concerns. Given the increasing prevalence of media use among German children, it is crucial to have a valid tool to assess problematic media use. The present study validated the 9-item short form of the problematic media use measure (Domoff et al., 2019) in a German sample of N = 240 parents of 4-16-year-old children and explored its relationship with child and parental mental health. Parents completed questionnaires on their child’s problematic media use, psychosocial functioning, their own mental health and media use online. The German version of the PMUM-SF demonstrated high internal consistency, and good convergent and incremental validity. Problematic media use was significantly associated with age and with child functioning such as externalizing and internalizing problems. Furthermore, parental media use and parental stress and depression were positively correlated with child problematic media use. The study thus supports the use of the German version of the PMUM-SF as a measure of problematic media use in children ages 4 through 16 years old.