The Old Catholic Church affirms that all humans inherit both the sin of Adam and the guilt of Adam's transgression. This inherited sinful condition is transmitted through human generation and affects all persons except Christ and Mary (who is affirmed as immaculate in most branches). Original sin involves both guilt (culpa) and corruption (poena): legal culpability and corrupted nature.

The consequences of original sin—mortality, ignorance, concupiscence (inclination toward sin)—are universal. Infants, though lacking personal actual sin, still bear the stain of original sin and require baptism for cleansing and regeneration. Baptism is the means through which original sin is forgiven and the soul is restored to grace.

This classic Catholic anthropology understands human nature as damaged but not wholly corrupt; the intellect and will, while wounded, retain some capacity to recognize good and choose it (with grace's assistance). Mary's Immaculate Conception—her preservation from original sin by divine grace—is affirmed by most Old Catholic branches, protecting both her dignity as Theotokos and the necessity of Christ's redemption as the universal remedy for sin.