Even though the causes of suicide may be rooted in childhood, it is unknown how socioeconomic position (SEP) in childhood is related to suicide in adulthood. We describe the association between childhood SEP and suicide mortality in adulthood in Norway using registry data on 613807 Norwegians born in 1955-1965. Data on 1013 suicide deaths between 1990 and 2001 were linked to data on SEP indicators, using Cox regression. Suicide mortality was higher among women with high childhood SEP than among women with low childhood SEP. This association was explained in part by family situation in adulthood, but not by adult SEP. For males, after adjustment for adult SEP, we observed a similar but weaker association between suicide and childhood SEP. We discuss several mechanisms which may explain the direct positive association of childhood SEP with suicide mortality in adulthood, especially among females. These are downward mobility, not meeting high demands set by highly educated parents, psychological distress, mental disorder, gender differences and social networks and norms.