The Old Catholic Church affirms that Christian doctrine comes from Scripture and Sacred Tradition together, not from Scripture alone. The apostolic deposit of faith was transmitted through both written Scripture and oral tradition ('the traditions of the elders' mentioned by Paul). The early church's understanding of apostolic faith is preserved in the writings of the Church Fathers, the decisions of the ecumenical councils (up to Nicaea II, 787 AD), and the ongoing life of the church.

However, the Old Catholic Church rejects the Roman Catholic claim that the Pope possesses an extraordinary magisterium capable of infallibly defining new doctrine. The church affirms development of doctrine (particularly through the work of theologians and synodical decisions), but this is not new revelation—it is the deepening understanding of apostolic faith guided by the Spirit. All doctrinal development must be consonant with Scripture and the witness of the Fathers.

Tradition is living and developing, yet bounded by apostolicity. Private revelations, mystical experiences, and prophetic utterances are not binding for the church. The Spirit's work in guiding the church into truth is discerned communally through bishops, theologians, and faithful, not through isolated individuals. This balances Scripture's primacy with the church's living authority to interpret and apply it.