Christadelphians reject the Augustinian doctrine of original sin as traditionally understood in Western Christianity — the teaching that Adam's guilt is directly imputed to all his descendants and that all humans are born in a state of legal condemnation for Adam's specific act. In Christadelphian theology, Adam's sin introduced mortality (physical death) and the tendency toward sin into the human race, but not inherited judicial guilt. Each person is responsible for their own sins, not for Adam's.

This position is connected to the Christadelphian denial of an immortal soul and their understanding of human nature. Human beings are mortal creatures who die because of the Fall, not immortal souls condemned to eternal punishment for inherited guilt. The problem that Christ's death addresses is not primarily legal guilt inherited from Adam but the reality of human sinfulness and mortality that results from living in a fallen world with a nature prone to sin.

Christadelphians also apply this to their understanding of Jesus: he inherited the mortal, sinful nature (the tendency toward sin) from his human mother, but not personal guilt. He overcame this nature through perfect obedience, making him the ideal sacrifice. This view differs from both the Roman Catholic teaching on original sin and the Reformed teaching on total depravity with imputed Adamic guilt, while affirming that all humans do in fact sin and need redemption.