Although it is widely assumed that avoidant personality disorder (AvPD) originates in childhood, there is little prospective research to substantiate this claim. We therefore aimed to determine whether presumed childhood risk factors predict AvPD traits at 16 years. A population-based sample (n = 1,077; 50.9% female) from the 2003 and 2004 birth cohorts in (blinded for review) Norway was examined biennially from 4 to 16 years. The number of AvPD traits at the age of 16 was assessed with the structured clinical interview for DSM-5 personality disorders and regressed on the intercept and growth in child risk and protective factors until the age of 14. The prevalence of AvPD at the age of 16 was 3.2% (95% CI: 2.2-4.1). Higher levels and an increased number of social anxiety symptoms over time, as well as increased negative affectivity/neuroticism, predicted a higher number of AvPD traits. When the levels and changes in these factors were adjusted for, less and decreasing extraversion forecasted more AvPD traits, as did declining self-worth, higher levels of parental AvPD traits, and increased onlooking behavior. Neuroticism, low extraversion, social anxiety symptoms, passive onlooking behavior, and low self-worth predicted a higher number of AvPD traits in adolescence, as did more AvPD traits in parents. Efforts to enhance self-worth, reduce social anxiety, and promote peer interaction among onlooking children may reduce the development of AvPD traits in adolescence.