Why do Catholic priests wear a roman collar? This tradition developed in the 1500s. Priests already wore special clothes (the cassock) and the fashionable collars of the time were adapted for priestly use. The roman collar is still worn by priests today as a sign of their vocation and service to the Church.
When a priest is ordained in the sacrament of Holy Orders, he receives special graces and abilities. He can change bread and wine into the Body and Blood of Christ in the Mass and he can forgive sins in the sacrament of Penance. The priest is able to do these things because he acts "in persona Christi." That means the priest acts in the person of Christ. He is Jesus' special representative on earth, and so dresses in a special way so we can know that he is a priest.
Just as humans are both body and soul, so are the rituals and symbols of the Church a mix of internal and external signs. Husbands and wives wear wedding rings to show their union and devotion. Priests, deacons, and seminarians wear collars and other clerical clothing to show their union with Christ and His Church.
Everyone who sees a priest wearing a collar knows that he is part of the Catholic Church. It inspires people to think of eternal things, and so the priest can evangelize even with the way he dresses.
Plus, when a priest is recognized because of his collar, he can help in emergency situations. People will know who to ask for help or for the sacraments, especially Confession and Anointing of the Sick, if there is an emergency.
So the roman collar is sign of a priest's vocation and dedication. Whenever he wears his collar, the priest serves as a visible sign of God and the Church in the world.
