Adults form highly influential impressions about how trustworthy someone is from a mere glance at their face. Given their social and adaptive influence, the question emerges of how trust impressions develop. Following renewed interest, some mixed findings, and debate around their origins, this paper systematically reviews and meta-analyses research on the maturity of children's face-based trust impressions. Results from 10 studies (representing 1325 children aged 3-12, and 851 adults aged 17-81, across White, Asian, and Black ethnicities, and both sexes) suggest beginnings of a mature trust impression system exist in 3-to 5-year-olds. Meta-analysis reveals trust impressions develop across childhood and show adult-like patterns between 10 and 13 years. Outstanding questions in the field are identified.