Is the Bible the only source of divine revelation for Catholics?

No. Catholic teaching holds that divine revelation is transmitted through two inseparable channels: Sacred Scripture and Sacred Tradition, both interpreted authentically by the Church's Magisterium. The Bible itself is a product of the Church and cannot be properly understood apart from the living Tradition from which it arose.

The Role of the Magisterium

The Magisterium is not above the Word of God but serves it, drawing from the one treasury of divine revelation to propose defined doctrine for the belief of the faithful (CCC 86).