<jats:title>Abstract</jats:title>
          <jats:p>Preventing loneliness is a significant goal due to its association with long-term negative effects on both mental and physical health. This German longitudinal study used three assessment points to examine predictors of emotional loneliness—defined as the absence of close, trusting relationships—in young adulthood (T3: age 22), based on factors assessed in early childhood (T1: age 4) and adolescence (T2: age 14). Utilizing data from 224 families, regression models were employed to identify child and parent risk factors—such as child and parent mental health problems, parent dysfunctional parenting, child adverse childhood experiences, child problematic internet use, and child experiences of school bullying—to predict child emotional loneliness. Emotional loneliness was measured through self-reports by adolescents/young adults and external reports provided by parents. Over 25% of adolescents reported emotional loneliness, a figure that increased to 50% in young adulthood during the pandemic. Experiencing loneliness in adolescence was associated with a significantly higher likelihood of feeling lonely again in emerging adulthood. Parents tend to underestimate their children’s feelings of loneliness. Lower levels of childhood externalizing mental health problems and higher levels of maternal dysfunctional parenting were associated with an increased likelihood of loneliness in adolescence. Only adolescent mental health problems predicted loneliness in emerging adulthood. Additionally, more adverse childhood experiences and higher levels of compulsive internet use during adolescence were linked to more adolescent mental health problems, identifying potential indirect targets for the prevention of loneliness. In contrast, paternal factors did not significantly contribute to the prediction of emotional loneliness in this sample. Effective strategies may include enhancing parenting practices and increasing awareness of child mental health problems, mitigating adverse childhood experiences, and reducing excessive internet use.</jats:p>