Prenatal androgen exposure has been associated with aggressive behavior in adults. It is less clear whether this association holds for childhood externalizing behavior. This study tests the hypothesis that increased prenatal androgen exposure is associated with aggressive behavior and attention problems in childhood. The ratio of the length of the second finger digit relative to the fourth digit, which is a marker for prenatal testosterone exposure, was assessed in 239 male and female fifth grade schoolchildren from Jintan, China, together with parent and teacher ratings of aggression and attention problems. Increased aggression and attention problems were both significantly associated with a lower ratio of the length of the second finger digit relative to the fourth digit ratios in boys but not girls. The effects remained significant after controlling for early adversity. These findings are the first to establish a relationship between an indirect indicator of fetal androgen exposure and any child psychopathology in Chinese children, and the observed effect size in boys was stronger than in male adults in Western studies. The results provide limited cross-cultural support for the importance of prenatal androgen exposure in contributing to the development of externalizing behavior problems in children, and they suggest that such effects may be specific to boys who may be relatively more vulnerable to early prenatal influences.