The font and the high altar of the Cathedral were both obtained through the Archbishop of Agra, India, where the Taj Mahal is located, at the request of Cardinal Gibbons. The floral designs are similar to those found in palaces and monuments of the Mogul Empire.

According to tradition, St. Matthew preached in Ethiopia after the resurrection of Christ. The mosaic at the west end of the Baptistry (pictured left) shows the saint baptizing an Ethiopian.

In front of the stained glass windows on the south wall is the Ambry, or Holy Oil Cabinet, which contains the three Sacred Oils used in the sacramental life of the Church: the Oil of Catechumens, the Oil of the Sick, and the Sacred Chrism. Each year on the Monday of Holy Week, Cardinal McCarrick blesses the new oils at the Chrism Mass. The oils are then taken by the priests and deacons to the parishes throughout the Archdiocese of Washington.

The Ambry was designed by Thomas Stehle and fabricated by Philip Duck. It is made of beveled glass and acacia wood and was designed to compliment the marble baptismal font.

The mosaic on the north wall (pictured left) recalls the description in the Gospel of John, chapter 5, of the angel disturbing the waters of the pool in Bethsaida. The sick, the blind, and the lame gathered at the pool. The first to enter the pool after the disturbance of the waters was cured. Jesus visited this place and cured a lame man, who had not been able to reach the waters. St. John recounts this miracle as a sign of Jesus’ power. The saving power of Jesus is present in the Sacrament of Baptism.

The two mosaics are the work of John de Rosen, who also designed the exterior mosaic above the entrance of the Cathedral and the mosaic in the Blessed Sacrament Chapel behind the tabernacle.